Author name code: unruh
ADS astronomy entries on 2022-09-14
author:"Unruh, Yvonne" 
------------------------------------------------------------------------  

Title: Making the Most of Transmission Spectra in Light of Stellar
Activity: Needs Identified by ExoPAG's Study Analysis Group 21
Authors: Rackham, Benjamin V.; Espinoza, Néstor; Berdyugina, Svetlana
   V.; Korhonen, Heidi; MacDonald, Ryan J.; Montet, Benjamin T.; Morris,
   Brett M.; Oshagh, Mahmoudreza; Shapiro, Alexander I.; Unruh, Yvonne
   C.; Quintana, Elisa V.; Zellem, Robert T.; SAG 21 Committee
Bibcode: 2022BAAS...54e4404R
Altcode:
  Transmission spectroscopy, a method for studying exoplanetary
  atmospheres by measuring the wavelength-dependent radius of a planet as
  it transits its star, relies on a precise understanding of the spectrum
  of the star being occulted. However, stars are not homogeneous,
  constant light sources but have temporally evolving photospheres
  and chromospheres with inhomogeneities like spots, faculae, and
  plages. Study Analysis Group 21 (SAG21) of NASA's Exoplanet Exploration
  Program Analysis Group (ExoPAG) was organized to study the effect
  of stellar photospheric heterogeneity on space-based transmission
  spectroscopy. This SAG brought together an interdisciplinary team
  of more than 100 scientists, with observers and theorists from the
  heliophysics, stellar astrophysics, planetary science, and exoplanetary
  atmosphere research communities, to study the current needs that can be
  addressed in this context to make the most of transit studies from NASA
  facilities like HST and JWST. Here we report on the main conclusions
  of this analysis, highlighting needs to be addressed and mitigation
  efforts underway. The analysis produced 14 findings, which fall into
  three Science Themes that encompass (1) how the Sun is used as our best
  laboratory to calibrate our understanding of stellar heterogeneities
  ("The Sun as the Stellar Benchmark"), (2) how stars other than the Sun
  extend our knowledge of heterogeneities ("Surface Heterogeneities of
  Other Stars"), and (3) how to incorporate information gathered for the
  Sun and other stars into transit studies ("Mapping Stellar Knowledge
  to Transit Studies"). Addressing the needs identified through this
  large community effort will ensure that we can optimally leverage
  space-based transmission spectra in light of stellar activity.

Title: Energy deposition in Saturn's equatorial upper atmosphere
Authors: Chadney, J. M.; Koskinen, T. T.; Hu, X.; Galand, M.; Lavvas,
   P.; Unruh, Y. C.; Serigano, J.; Hörst, S. M.; Yelle, R. V.
Bibcode: 2022Icar..37214724C
Altcode: 2021arXiv211008014C
  We construct Saturn equatorial neutral temperature and density profiles
  of H, H<SUB>2</SUB>, He, and CH<SUB>4</SUB>, between 10<SUP>-12</SUP>
  and 1 bar using measurements from Cassini's Ion Neutral Mass
  Spectrometer (INMS) taken during the spacecraft's final plunge into
  Saturn's atmosphere on 15 September 2017, combined with previous
  deeper atmospheric measurements from the Cassini Composite InfraRed
  Spectrometer (CIRS) and from the UltraViolet Imaging Spectrograph
  (UVIS). These neutral profiles are fed into an energy deposition
  model employing soft X-ray and Extreme UltraViolet (EUV) solar fluxes
  at a range of spectral resolutions (Δλ = 4 × 10<SUP>-3</SUP> nm
  to 1 nm) assembled from TIMED/SEE, from SOHO/SUMER, and from the
  Whole Heliosphere Interval (WHI) quiet Sun campaign. Our energy
  deposition model calculates ion production rate profiles through
  photo-ionisation and electron-impact ionisation processes, as well as
  rates of photo-dissociation of CH<SUB>4</SUB>. The ion reaction rate
  profiles we determine are important to obtain accurate ion density
  profiles, meanwhile methane photo-dissociation is key to initiate
  complex organic chemical processes. We assess the importance of spectral
  resolution in the energy deposition model by using a high-resolution
  H<SUB>2</SUB> photo-absorption cross section, which has the effect of
  producing additional ionisation peaks near 800 km altitude. We find
  that these peaks are still formed when using low-resolution (Δλ =
  1 nm) or mid-resolution (Δλ = 0 . 1 nm) solar spectra, as long as
  high-resolution cross sections are included in the model.

Title: Final Report for SAG 21: The Effect of Stellar Contamination
    on Space-based Transmission Spectroscopy
Authors: Rackham, Benjamin V.; Espinoza, Néstor; Berdyugina, Svetlana
   V.; Korhonen, Heidi; MacDonald, Ryan J.; Montet, Benjamin T.; Morris,
   Brett M.; Oshagh, Mahmoudreza; Shapiro, Alexander I.; Unruh, Yvonne C.;
   Quintana, Elisa V.; Zellem, Robert T.; Apai, Dániel; Barclay, Thomas;
   Barstow, Joanna K.; Bruno, Giovanni; Carone, Ludmila; Casewell, Sarah
   L.; Cegla, Heather M.; Criscuoli, Serena; Fischer, Catherine; Fournier,
   Damien; Giampapa, Mark S.; Giles, Helen; Iyer, Aishwarya; Kopp, Greg;
   Kostogryz, Nadiia M.; Krivova, Natalie; Mallonn, Matthias; McGruder,
   Chima; Molaverdikhani, Karan; Newton, Elisabeth R.; Panja, Mayukh;
   Peacock, Sarah; Reardon, Kevin; Roettenbacher, Rachael M.; Scandariato,
   Gaetano; Solanki, Sami; Stassun, Keivan G.; Steiner, Oskar; Stevenson,
   Kevin B.; Tregloan-Reed, Jeremy; Valio, Adriana; Wedemeyer, Sven;
   Welbanks, Luis; Yu, Jie; Alam, Munazza K.; Davenport, James R. A.;
   Deming, Drake; Dong, Chuanfei; Ducrot, Elsa; Fisher, Chloe; Gilbert,
   Emily; Kostov, Veselin; López-Morales, Mercedes; Line, Mike; Močnik,
   Teo; Mullally, Susan; Paudel, Rishi R.; Ribas, Ignasi; Valenti, Jeff A.
Bibcode: 2022arXiv220109905R
Altcode:
  Study Analysis Group 21 (SAG21) of the Exoplanet Exploration Program
  Analysis Group (ExoPAG) was organized to study the effect of stellar
  contamination on space-based transmission spectroscopy, a method for
  studying exoplanetary atmospheres by measuring the wavelength-dependent
  radius of a planet as it transits its star. Transmission spectroscopy
  relies on a precise understanding of the spectrum of the star being
  occulted. However, stars are not homogeneous, constant light sources
  but have temporally evolving photospheres and chromospheres with
  inhomogeneities like spots, faculae, and plages. This SAG has brought
  together an interdisciplinary team of more than 100 scientists, with
  observers and theorists from the heliophysics, stellar astrophysics,
  planetary science, and exoplanetary atmosphere research communities,
  to study the current needs that can be addressed in this context to
  make the most of transit studies from current NASA facilities like
  HST and JWST. The analysis produced 14 findings, which fall into
  three Science Themes encompassing (1) how the Sun is used as our best
  laboratory to calibrate our understanding of stellar heterogeneities
  ("The Sun as the Stellar Benchmark"), (2) how stars other than the Sun
  extend our knowledge of heterogeneities ("Surface Heterogeneities of
  Other Stars") and (3) how to incorporate information gathered for the
  Sun and other stars into transit studies ("Mapping Stellar Knowledge
  to Transit Studies").

Title: MPS-ATLAS: A fast all-in-one code for synthesising stellar
    spectra
Authors: Witzke, V.; Shapiro, A. I.; Cernetic, M.; Tagirov, R. V.;
   Kostogryz, N. M.; Anusha, L. S.; Unruh, Y. C.; Solanki, S. K.; Kurucz,
   R. L.
Bibcode: 2021A&A...653A..65W
Altcode: 2021arXiv210513611W
  Context. Stellar spectral synthesis is essential for various
  applications, ranging from determining stellar parameters to
  comprehensive stellar variability calculations. New observational
  resources as well as advanced stellar atmosphere modelling, taking three
  dimensional effects from radiative magnetohydrodynamics calculations
  into account, require a more efficient radiative transfer. <BR /> Aims:
  For accurate, fast and flexible calculations of opacity distribution
  functions (ODFs), stellar atmospheres, and stellar spectra, we developed
  an efficient code building on the well-established ATLAS9 code. The new
  code also paves the way for easy and fast access to different elemental
  compositions in stellar calculations. <BR /> Methods: For the generation
  of ODF tables, we further developed the well-established DFSYNTHE code
  by implementing additional functionality and a speed-up by employing
  a parallel computation scheme. In addition, the line lists used can be
  changed from Kurucz's recent lists. In particular, we implemented the
  VALD3 line list. <BR /> Results: A new code, the Merged Parallelised
  Simplified ATLAS, is presented. It combines the efficient generation of
  ODF, atmosphere modelling, and spectral synthesis in local thermodynamic
  equilibrium, therefore being an all-in-one code. This all-in-one code
  provides more numerical functionality and is substantially faster
  compared to other available codes. The fully portable MPS-ATLAS code
  is validated against previous ATLAS9 calculations, the PHOENIX code
  calculations, and high-quality observations.

Title: Forward modelling of Kepler-band variability due to faculae
    and spots
Authors: Johnson, Luke J.; Norris, Charlotte M.; Unruh, Yvonne C.;
   Solanki, Sami K.; Krivova, Natalie; Witzke, Veronika; Shapiro,
   Alexander I.
Bibcode: 2021MNRAS.504.4751J
Altcode: 2021arXiv210411544J; 2021MNRAS.tmp.1190J
  Variability observed in photometric light curves of late-type stars (on
  time-scales longer than a day) is a dominant noise source in exoplanet
  surveys and results predominantly from surface manifestations of stellar
  magnetic activity, namely faculae and spots. The implementation of
  faculae in light-curve models is an open problem, with scaling typically
  based on spectra equivalent to hot stellar atmospheres or assuming a
  solar-derived facular contrast. We modelled rotational (single period)
  light curves of active G2, K0, M0, and M2 stars, with Sun-like surface
  distributions and realistic limb-dependent contrasts for faculae and
  spots. The sensitivity of light-curve variability to changes in model
  parameters such as stellar inclination, feature area coverage, spot
  temperature, facular region magnetic flux density, and active band
  latitudes is explored. For our light-curve modelling approach we used
  ACTRESS, a geometrically accurate model for stellar variability. ACTRESS
  generates two-sphere maps representing stellar surfaces and populates
  them with user-prescribed spot and facular region distributions. From
  this, light curves can be calculated at any inclination. Quiet star limb
  darkening and limb-dependent facular contrasts were derived from MURaM
  3D magnetoconvection simulations using ATLAS9. 1D stellar atmosphere
  models were used for the spot contrasts. We applied ACTRESS in Monte
  Carlo simulations, calculating light-curve variability amplitudes in
  the Kepler band. We found that, for a given spectral type and stellar
  inclination, spot temperature and spot area coverage have the largest
  effect on variability of all simulation parameters. For a spot coverage
  of $1{{\ \rm per\ cent}}$, the typical variability of a solar-type
  star is around 2 parts per thousand. The presence of faculae clearly
  affects the mean brightness and light-curve shape, but has relatively
  little influence on the variability.

Title: Simulating Variability due to Faculae and Spots on GKM Stars
Authors: Johnson, Luke; Unruh, Yvonne; Norris, Charlotte; Solanki,
   Sami; Krivova, Natalie; Witzke, Veronika; Shapiro, Alexander
Bibcode: 2020EPSC...14..844J
Altcode:
  Stellar variability is a dominant noise source in exoplanet surveys
  and results largely from the presence of photospheric faculae and
  spots. The implementation of faculae in lightcurve models is an open
  problem, with scaling based on spectra equivalent to hot stellar
  atmospheres or assuming a solar-derived facular contrast. We model the
  lightcurves of active late-type stars as they rotate, using emergent
  intensity spectra calculated from 3D magnetoconvection simulations
  of G, K and M-type stellar atmosphere regions at different viewing
  angles to reproduce centre-to-limb brightness variations. We present
  mean expected variability levels for several cases and compare with
  solar and stellar observations. We also investigate the wavelength
  dependence of variability. Fig. 1: Example of our geometrically
  accurate lightcurve modelling approach. Top: normalised intensity
  maps of a limb darkened, solar-type star viewed in the \textit{Kepler}
  band at rotational phase 0.5 with stellar inclinations 90 deg (left)
  and 30 deg (right). At 90 deg, the star is viewed equator-on. Middle:
  Corresponding lightcurves calculated at inclinations 90 deg (black line)
  and 30 deg (red line). Bottom: HealPix map representing the active
  stellar surface, cosine-scaled in latitude and flattened in longitude
  to resemble a solar synoptic map. The quiet photosphere is displayed
  in orange, facular regions are bright yellow and spot regions are dark
  blue. The crosses represent the centres of the stellar discs in the
  top panel. Fig. 2: Example showing simulated lightcurves calculated
  at different wavelengths. Rotational lightcurves are on the left,
  transit lightcurves on the right. In the centre, one hemisphere of the
  simulated stellar surface is shown, with a quarter of the disc shown
  in each wavelength band. 'Giant' spots and facular regions are used
  in this example. The transit path is highlighted in grey.

Title: Connecting measurements of solar and stellar brightness
    variations
Authors: Nèmec, N. -E.; Işık, E.; Shapiro, A. I.; Solanki, S. K.;
   Krivova, N. A.; Unruh, Y.
Bibcode: 2020A&A...638A..56N
Altcode: 2020arXiv200406974N
  Context. A comparison of solar and stellar brightness variations is
  hampered by the difference in spectral passbands that are used in
  observations, and also by the possible difference in the inclination
  of the solar and stellar rotation axes from the line of sight. <BR />
  Aims: We calculate the rotational variability of the Sun as it would
  be measured in passbands used for stellar observations. In particular,
  we consider the filter systems used by the CoRoT, Kepler, TESS, and
  Gaia space missions. We also quantify the effect of the inclination
  of the rotation axis on the solar rotational variability. <BR />
  Methods: We employed the spectral and total irradiance reconstruction
  (SATIRE) model to calculate solar brightness variations in different
  filter systems as observed from the ecliptic plane. We then combined
  the simulations of the surface distribution of the magnetic features
  at different inclinations using a surface flux transport model with
  the SATIRE calculations to compute the dependence of the variability
  on the inclination. <BR /> Results: For an ecliptic-bound observer,
  the amplitude of the solar rotational variability, as observed in
  the total solar irradiance (TSI), is 0.68 mmag (averaged over solar
  cycles 21-24). We obtained corresponding amplitudes in the Kepler
  (0.74 mmag), CoRoT (0.73 mmag), TESS (0.62 mmag), Gaia G (0.74 mmag),
  Gaia G<SUB>RP</SUB> (0.62 mmag), and Gaia G<SUB>BP</SUB> (0.86 mmag)
  passbands. Decreasing the inclination of the rotation axis decreases
  the rotational variability. For a sample of randomly inclined stars,
  the variability is on average 15% lower in all filter systems we
  considered. This almost compensates for the difference in amplitudes
  of the variability in TSI and Kepler passbands, making the amplitudes
  derived from the TSI records an ideal representation of the solar
  rotational variability for comparison to Kepler stars with unknown
  inclinations. <BR /> Conclusions: The TSI appears to be a relatively
  good measure of solar variability for comparisons with stellar
  measurements in the CoRoT, Kepler, TESS Gaia G, and Gaia G<SUB>RP</SUB>
  filters. Whereas the correction factors can be used to convert the
  variability amplitude from solar measurements into the values expected
  for stellar missions, the inclination affects the shapes of the light
  curves so that a much more sophisticated correction than simple scaling
  is needed to obtain light curves out of the ecliptic for the Sun.

Title: IGAPS: the merged IPHAS and UVEX optical surveys of the
    northern Galactic plane
Authors: Monguió, M.; Greimel, R.; Drew, J. E.; Barentsen, G.;
   Groot, P. J.; Irwin, M. J.; Casares, J.; Gänsicke, B. T.; Carter,
   P. J.; Corral-Santana, J. M.; Gentile-Fusillo, N. P.; Greiss, S.; van
   Haaften, L. M.; Hollands, M.; Jones, D.; Kupfer, T.; Manser, C. J.;
   Murphy, D. N. A.; McLeod, A. F.; Oosting, T.; Parker, Q. A.; Pyrzas,
   S.; Rodríguez-Gil, P.; van Roestel, J.; Scaringi, S.; Schellart, P.;
   Toloza, O.; Vaduvescu, O.; van Spaandonk, L.; Verbeek, K.; Wright,
   N. J.; Eislöffel, J.; Fabregat, J.; Harris, A.; Morris, R. A. H.;
   Phillipps, S.; Raddi, R.; Sabin, L.; Unruh, Y.; Vink, J. S.; Wesson,
   R.; Cardwell, A.; de Burgos, A.; Cochrane, R. K.; Doostmohammadi,
   S.; Mocnik, T.; Stoev, H.; Suárez-Andrés, L.; Tudor, V.; Wilson,
   T. G.; Zegmott, T. J.
Bibcode: 2020A&A...638A..18M
Altcode: 2020arXiv200205157M
  The INT Galactic Plane Survey (IGAPS) is the merger of the optical
  photometric surveys, IPHAS and UVEX, based on data from the Isaac
  Newton Telescope (INT) obtained between 2003 and 2018. Here, we
  present the IGAPS point source catalogue. It contains 295.4 million
  rows providing photometry in the filters, i, r, narrow-band Hα,
  g, and U<SUB>RGO</SUB>. The IGAPS footprint fills the Galactic
  coordinate range, |b| &lt; 5° and 30° &lt; ℓ &lt; 215°. A
  uniform calibration, referred to as the Pan-STARRS system, is
  applied to g, r, and i, while the Hα calibration is linked to r
  and then is reconciled via field overlaps. The astrometry in all
  five bands has been recalculated in the reference frame of Gaia Data
  Release 2. Down to i ∼ 20 mag (Vega system), most stars are also
  detected in g, r, and Hα. As exposures in the r band were obtained
  in both the IPHAS and UVEX surveys, typically a few years apart,
  the catalogue includes two distinct r measures, r<SUB>I</SUB> and
  r<SUB>U</SUB>. The r 10σ limiting magnitude is approximately 21,
  with median seeing of 1.1 arcsec. Between approximately 13th and 19th
  mag in all bands, the photometry is internally reproducible to within
  0.02 mag. Stars brighter than r = 19.5 mag are tested for narrow-band
  Hα excess signalling line emission, and for variation exceeding
  |r<SUB>I</SUB> - r<SUB>U</SUB>| = 0.2 mag. We find and flag 8292
  candidate emission line stars and over 53 000 variables (both at &gt;
  5σ confidence). <P />The catalogue of 174 columns in total and full
  Tables D.1-D.4 are only available at the CDS via anonymous ftp to <A
  href="http://cdsarc.u-strasbg.fr/">http://cdsarc.u-strasbg.fr</A>ftp://130.79.128.5)
  or via <A
  href="http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/638/A18">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/638/A18</A>

Title: VizieR Online Data Catalog: IGAPS. merged IPHAS and UVEX of
    northern Galactic plane (Monguio+, 2020)
Authors: Monguio, M.; Greimel, R.; Drew, J. E.; Barentsen, G.;
   Groot, P. J.; Irwin, M. J.; Casares, J.; Gaensicke, B. T.; Carter,
   P. J.; Corral-Santana, J. M.; Gentile-Fusillo, N. P.; Greiss, S.; van
   Haaften, L. M.; Hollands, M.; Jones, D.; Kupfer, T.; Manser, C. J.;
   Murphy, D. N. A.; McLeod, A. F.; Oosting, T.; Parker, Q. A.; Pyrzas,
   S.; Rodriguez-Gil, P.; van Roestel, J.; Scaringi, S.; Schellart, P.;
   Toloza, O.; Vaduvescu, O.; van Spaandonk, L.; Verbeek, K.; Wright,
   N. J.; Eisloeel, J.; Fabregat, J.; Harris, A.; Morris, R. A. H.;
   Phillipps, S.; Raddi, R.; Sabin, L.; Unruh, Y.; S Vink, J.; Wesson,
   R.; Cardwell, A.; de Burgos, A.; Cochrane, R. K.; Doostmohammadi, S.;
   Mocnik, T.; Stoev, H.; Suarez-Andres, L.; Tudor, V.; Wilson, T. G.;
   Zegmott, T. J.
Bibcode: 2020yCat.5165....0M
Altcode:
  The INT Galactic Plane Survey (IGAPS) was formed from merging the
  IPHAS (Drew et al., 2005MNRAS.362..753D) and UVEX (Groot et al.,
  2009MNRAS.399..323G, Cat. J/MNRAS/399/323) surveys of the northern
  Galactic plane, based on data from the Isaac Newton Telescope (INT)
  obtained between 2003 and 2018. It is a catalogue of 174 columns and
  almost 300 million rows, spanning the r magnitude range from 12-13th
  mag down to 21st mag (10σ). The astrometry in all five photometric
  bands has been placed in the Gaia DR2 reference frame. Broadband g,
  r, and i have been uniformly calibrated using PanSTARRS data resting
  on that project's 'Ubercal' (Magnier et al. 2013ApJS..205...20M). We
  estimate the reproducibility of the photometry in these bands (and in
  Hα) to be in the region of 0.02mag at magnitudes brighter than 19th
  mag. <P />(1 data file).

Title: Readdressing the UV solar variability with SATIRE-S: non-LTE
    effects
Authors: Tagirov, R. V.; Shapiro, A. I.; Krivova, N. A.; Unruh, Y. C.;
   Yeo, K. L.; Solanki, S. K.
Bibcode: 2019A&A...631A.178T
Altcode: 2019arXiv190911736T
  Context. Solar spectral irradiance (SSI) variability is one of the key
  inputs to models of the Earth's climate. Understanding solar irradiance
  fluctuations also helps to place the Sun among other stars in terms of
  their brightness variability patterns and to set detectability limits
  for terrestrial exoplanets. <BR /> Aims: One of the most successful
  and widely used models of solar irradiance variability is Spectral
  And Total Irradiance REconstruction model (SATIRE-S). It uses spectra
  of the magnetic features and surrounding quiet Sun that are computed
  with the ATLAS9 spectral synthesis code under the assumption of local
  thermodynamic equilibrium (LTE). SATIRE-S has been at the forefront
  of solar variability modelling, but due to the limitations of the LTE
  approximation its output SSI has to be empirically corrected below
  300 nm, which reduces the physical consistency of its results. This
  shortcoming is addressed in the present paper. <BR /> Methods: We
  replaced the ATLAS9 spectra of all atmospheric components in SATIRE-S
  with spectra that were calculated using the Non-LTE Spectral SYnthesis
  (NESSY) code. To compute the spectrum of the quiet Sun and faculae,
  we used the temperature and density stratification models of the FAL
  set. <BR /> Results: We computed non-LTE contrasts of spots and faculae
  and combined them with the corresponding fractional disc coverages,
  or filling factors, to calculate the total and spectral irradiance
  variability during solar cycle 24. The filling factors have been derived
  from solar full-disc magnetograms and continuum images recorded by
  the Helioseismic and Magnetic Imager on Solar Dynamics Observatory
  (SDO/HMI). <BR /> Conclusions: The non-LTE contrasts yield total and
  spectral solar irradiance variations that are in good agreement with
  empirically corrected LTE irradiance calculations. This shows that
  the empirical correction applied to the SATIRE-S total and spectral
  solar irradiance is consistent with results from non-LTE computations.

Title: What do astronomers want from the STFC?
Authors: Serjeant, Stephen; Bolton, James; Gandhi, Poshak; Helling,
   Christiane; Mazzali, Paolo; Stappers, Ben; Unruh, Yvonne; Verma,
   Aprajita
Bibcode: 2019A&G....60b2.13S
Altcode:
  Stephen Serjeant and the STFC's Astronomy Advisory Panel summarize
  community responses to its consultation on research priorities,
  undertaken in November 2018.

Title: ACTReSS: ACTive Rotating Star Simulator
Authors: Johnson, Luke Jonathan; Norris, Charlotte; Unruh, Yvonne;
   Solanki, Sami; Krivova, Natalie
Bibcode: 2018csss.confE..58J
Altcode:
  Variability of late-type stars on timescales of days or longer is
  largely due to magnetic surface features (starspots and faculae). We
  present ACTReSS, a software tool to calculate rotational lightcurves
  of stars. The model uses limb-dependent intensities derived from
  MURaM 3-D magneto-convection simulations (Beeck et al. 2014) for
  quiet stellar photospheres and bright active regions. This allows us
  to investigate the dependence of the flux variation on spectral type,
  inclination and wavelength.

Title: Reconstructing Total Solar Irradiance with the help of MHD
    simulations
Authors: Leng Yeo, Kok; Solanki, Sami; Noris, Charlotte; Unruh,
   Yvonne; Krivova, Natalie; Beeck, Benjamin
Bibcode: 2018EGUGA..20.8166L
Altcode:
  The variation in the solar irradiance is an important input into the
  climate system. Whereas it is commonly thought that solar irradiance
  variability is driven by the evolving surface magnetism, verifying this
  assumption has been more difficult. Making use of 3D MHD simulations
  of the solar atmosphere layers and state-of-the-art solar magnetograms
  from the Solar Dynamics Observatory, we present a model of total solar
  irradiance (TSI) that does not require any calibration of the modeled
  TSI by the measured TSI. I.e., the modeled irradiance variability
  is entirely independent of the observational record, except for the
  absolute level. The model replicates 95% of the observed variability
  between April 2010 and July 2016, leaving little scope for alternative
  drivers of solar irradiance variability, at least over the time scales
  examined (days to years).

Title: Effect of stellar flares on the upper atmospheres of HD
    189733b and HD 209458b
Authors: Chadney, J. M.; Koskinen, T. T.; Galand, M.; Unruh, Y. C.;
   Sanz-Forcada, J.
Bibcode: 2017A&A...608A..75C
Altcode: 2017arXiv171008365C
  Stellar flares are a frequent occurrence on young low-mass stars around
  which many detected exoplanets orbit. Flares are energetic, impulsive
  events, and their impact on exoplanetary atmospheres needs to be taken
  into account when interpreting transit observations. We have developed
  a model to describe the upper atmosphere of extrasolar giant planets
  (EGPs) orbiting flaring stars. The model simulates thermal escape from
  the upper atmospheres of close-in EGPs. Ionisation by solar radiation
  and electron impact is included and photo-chemical and diffusive
  transport processes are simulated. This model is used to study the
  effect of stellar flares from the solar-like G star <ASTROBJ>HD
  209458</ASTROBJ> and the young K star <ASTROBJ>HD 189733</ASTROBJ>
  on their respective planets, <ASTROBJ>HD 209458b</ASTROBJ> and
  <ASTROBJ>HD 189733b</ASTROBJ>. The <ASTROBJ>Sun</ASTROBJ> is used as
  a proxy for HD 209458, and <ASTROBJ>ɛ Eridani</ASTROBJ>, as a proxy
  for HD 189733. A hypothetical HD 209458b-like planet orbiting the very
  active M star <ASTROBJ>AU Microscopii</ASTROBJ> is also simulated. We
  find that the neutral upper atmosphere of EGPs is not significantly
  affected by typical flares on HD 209458 and HD 189733. Therefore,
  stellar flares alone would not cause large enough changes in planetary
  mass loss to explain the variations in HD 189733b transit depth seen
  in previous studies, although we show that it may be possible that
  an extreme stellar proton event could result in the required mass
  loss. Our simulations do however reveal an enhancement in electron
  number density in the ionosphere of these planets, the peak of which
  is located in the layer where stellar X-rays are absorbed. Electron
  densities are found to reach 2.2 to 3.5 times pre-flare levels and
  enhanced electron densities last from about 3 to 10 h after the
  onset of the flare, depending on the composition of the ionospheric
  layer. The strength of the flare and the width of its spectral energy
  distribution affect the range of altitudes in the ionosphere that see
  enhancements in ionisation. A large broadband continuum component in
  the XUV portion of the flaring spectrum in very young flare stars, such
  as AU Mic, results in a broad range of altitudes affected in planets
  orbiting this star. Indeed, as well as the X-ray absorption layer,
  the layer in which EUV photons are absorbed is also strongly enhanced.

Title: Spectral variability of photospheric radiation due to
    faculae. I. The Sun and Sun-like stars
Authors: Norris, Charlotte M.; Beeck, Benjamin; Unruh, Yvonne C.;
   Solanki, Sami K.; Krivova, Natalie A.; Yeo, Kok Leng
Bibcode: 2017A&A...605A..45N
Altcode: 2017arXiv170504455N
  Context. Stellar spectral variability on timescales of a day and
  longer, arising from magnetic surface features such as dark spots
  and bright faculae, is an important noise source when characterising
  extra-solar planets. Current 1D models of faculae do not capture the
  geometric properties and fail to reproduce observed solar facular
  contrasts. Magnetoconvection simulations provide facular contrasts
  accounting for geometry. <BR /> Aims: We calculate facular contrast
  spectra from magnetoconvection models of the solar photosphere with
  a view to improve (a) future parameter determinations for planets
  with early G type host stars and (b) reconstructions of solar spectral
  variability. <BR /> Methods: Regions of a solar twin (G2, log g = 4.44)
  atmosphere with a range of initial average vertical magnetic fields
  (100 to 500 G) were simulated using a 3D radiation-magnetohydrodynamics
  code, MURaM, and synthetic intensity spectra were calculated from
  the ultraviolet (149.5 nm) to the far infrared (160 000 nm) with the
  ATLAS9 radiative transfer code. Nine viewing angles were investigated
  to account for facular positions across most of the stellar disc. <BR
  /> Results: Contrasts of the radiation from simulation boxes with
  different levels of magnetic flux relative to an atmosphere with no
  magnetic field are a complicated function of position, wavelength
  and magnetic field strength that is not reproduced by 1D facular
  models. Generally, contrasts increase towards the limb, but at UV
  wavelengths a saturation and decrease are observed close to the
  limb. Contrasts also increase strongly from the visible to the UV;
  there is a rich spectral dependence, with marked peaks in molecular
  bands and strong spectral lines. At disc centre, a complex relationship
  with magnetic field was found and areas of strong magnetic field
  can appear either dark or bright, depending on wavelength. Spectra
  calculated for a wide variety of magnetic fluxes will also serve to
  improve total and spectral solar irradiance reconstructions.

Title: Solar Irradiance Variability is Caused by the Magnetic Activity
    on the Solar Surface
Authors: Yeo, K. L.; Solanki, S. K.; Norris, C. M.; Beeck, B.; Unruh,
   Y. C.; Krivova, N. A.
Bibcode: 2017PhRvL.119i1102Y
Altcode: 2017arXiv170900920Y
  The variation in the radiative output of the Sun, described in terms
  of solar irradiance, is important to climatology. A common assumption
  is that solar irradiance variability is driven by its surface
  magnetism. Verifying this assumption has, however, been hampered by
  the fact that models of solar irradiance variability based on solar
  surface magnetism have to be calibrated to observed variability. Making
  use of realistic three-dimensional magnetohydrodynamic simulations
  of the solar atmosphere and state-of-the-art solar magnetograms from
  the Solar Dynamics Observatory, we present a model of total solar
  irradiance (TSI) that does not require any such calibration. In doing
  so, the modeled irradiance variability is entirely independent of the
  observational record. (The absolute level is calibrated to the TSI
  record from the Total Irradiance Monitor.) The model replicates 95%
  of the observed variability between April 2010 and July 2016, leaving
  little scope for alternative drivers of solar irradiance variability
  at least over the time scales examined (days to years).

Title: VizieR Online Data Catalog: New OB star candidates in Carina
    Arm (Mohr-Smith+, 2015)
Authors: Mohr-Smith, M.; Drew, J. E.; Barentsen, G.; Wright, N. J.;
   Napiwotzki, R.; Corradi, R. L. M.; Eisloffel, J.; Groot, P.; Kalari,
   V.; Parker, Q. A.; Raddi, R.; Sale, S. E.; Unruh, Y. C.; Vink, J. S.;
   Wesson, R.
Bibcode: 2017yCat..74503855M
Altcode:
  We make use of the photometry from two VPHAS+ fields, numbered 1678 and
  1679, that are, respectively, centred on RA=10:18:10.91, DE=-58:03:52.3
  (J2000) and on RA=10:25:27.27, DE=-58:03:52.3 (J2000). These were
  observed in succession in the u, g and r filters on the night of 2012
  January 22. The red filter data in Hα, r and i were obtained on 2012
  April 29. <P />(2 data files).

Title: The VST Photometric Halpha Survey of the Southern Galactic
    Plane and Bulge (VPHAS+). Second VPHAS data release (DR2).
Authors: Drew, J. E.; Gonzales-Solares, E.; Greimel, R.; Irwin, M. J.;
   Kupcu Yoldas, A.; Lewis, J.; Barentsen, G.; Eisloffel, J.; Farnhill,
   H. J.; Martin, W. E.; Walsh, J. R.; Walton, N. A.; Mohr-Smith, M.;
   Raddi, R.; Sale, S. E.; Wright, N. J.; Groot, P.; Barlow, M. J.;
   Corradi, R. L. M.; Drake, J. J.; Fabregat, J.; Frew, D. J.; Gansicke,
   B. T.; Knigge, C.; Mampaso, A.; Morris, R. A. H.; Naylor, T.; Parker,
   Q. A.; Phillipps, S.; Ruhland, C.; Steeghs, D.; Unruh, Y. C.; Vink,
   J. S.; Wesson, R.; Zijlstra, A. A.
Bibcode: 2016yCat.2341....0D
Altcode:
  No abstract at ADS

Title: Modelling the Spectral Contrasts of Stellar Faculae.
Authors: Norris, Charlotte M.; Beeck, Benjamin; Unruh, Yvonne; Solanki,
   Sami; Yeo, Kok Leng; Krivova, Natalie
Bibcode: 2016csss.confE..63N
Altcode:
  Facular contrasts are an important parameter in modelling stellar
  variability and exoplanet transits. The ultimate goal of this work
  will be to model the contrasts of faculae for different spectral types
  and thus improve the modelling of solar and stellar photospheric
  variability. This is done by using a radiative transfer algorithm
  (ATLAS9) on magneto-convection simulations. Starting with solar twins,
  we derive facular contrasts as a function of limb angle and discuss
  their wavelength dependence.

Title: Reconstruction of spectral solar irradiance since 1700 from
    simulated magnetograms
Authors: Dasi-Espuig, M.; Jiang, J.; Krivova, N. A.; Solanki, S. K.;
   Unruh, Y. C.; Yeo, K. L.
Bibcode: 2016A&A...590A..63D
Altcode: 2016arXiv160502039D
  <BR /> Aims: We present a reconstruction of the spectral solar
  irradiance since 1700 using the SATIRE-T2 (Spectral And Total Irradiance
  REconstructions for the Telescope era version 2) model. This model
  uses as input magnetograms simulated with a surface flux transport
  model fed with semi-synthetic records of emerging sunspot groups. <BR
  /> Methods: The record of sunspot group areas and positions from the
  Royal Greenwich Observatory (RGO) is only available since 1874. We
  used statistical relationships between the properties of sunspot
  group emergence, such as the latitude, area, and tilt angle, and the
  sunspot cycle strength and phase to produce semi-synthetic sunspot
  group records starting in the year 1700. The semi-synthetic records
  are fed into a surface flux transport model to obtain daily simulated
  magnetograms that map the distribution of the magnetic flux in active
  regions (sunspots and faculae) and their decay products on the solar
  surface. The magnetic flux emerging in ephemeral regions is accounted
  for separately based on the concept of extended cycles whose length
  and amplitude are linked to those of the sunspot cycles through the
  sunspot number. The magnetic flux in each surface component (sunspots,
  faculae and network, and ephemeral regions) was used to compute the
  spectral and total solar irradiance (TSI) between the years 1700
  and 2009. This reconstruction is aimed at timescales of months or
  longer although the model returns daily values. <BR /> Results: We
  found that SATIRE-T2, besides reproducing other relevant observations
  such as the total magnetic flux, reconstructs the TSI on timescales
  of months or longer in good agreement with the PMOD composite of
  observations, as well as with the reconstruction starting in 1878
  based on the RGO-SOON data. The model predicts an increase in the TSI
  of 1.2<SUP>+0.2</SUP><SUB>-0.3</SUB> Wm<SUP>-2</SUP> between 1700
  and the present. The spectral irradiance reconstruction is in good
  agreement with the UARS/SUSIM measurements as well as the Lyman-α
  composite. <P />The complete total and spectral (115 nm-160 μm)
  irradiance reconstructions since 1700 will be available from <A
  href="http://www2.mps.mpg.de/projects/sun-climate/data.html">http://www2.mps.mpg.de/projects/sun-climate/data.html</A>

Title: The Sun as a planet-host star: proxies from SDO images for
    HARPS radial-velocity variations
Authors: Haywood, R. D.; Collier Cameron, A.; Unruh, Y. C.; Lovis,
   C.; Lanza, A. F.; Llama, J.; Deleuil, M.; Fares, R.; Gillon, M.;
   Moutou, C.; Pepe, F.; Pollacco, D.; Queloz, D.; Ségransan, D.
Bibcode: 2016MNRAS.457.3637H
Altcode: 2016arXiv160105651H
  The Sun is the only star whose surface can be directly resolved at
  high resolution, and therefore constitutes an excellent test case
  to explore the physical origin of stellar radial-velocity (RV)
  variability. We present HARPS observations of sunlight scattered
  off the bright asteroid 4/Vesta, from which we deduced the Sun's
  activity-driven RV variations. In parallel, the Helioseismic and
  Magnetic Imager instrument on board the Solar Dynamics Observatory
  provided us with simultaneous high spatial resolution magnetograms,
  Dopplergrams and continuum images of the Sun in the Fe I 6173 Å
  line. We determine the RV modulation arising from the suppression of
  granular blueshift in magnetized regions and the flux imbalance induced
  by dark spots and bright faculae. The rms velocity amplitudes of these
  contributions are 2.40 and 0.41 m s<SUP>-1</SUP>, respectively, which
  confirms that the inhibition of convection is the dominant source of
  activity-induced RV variations at play, in accordance with previous
  studies. We find the Doppler imbalances of spot and plage regions to be
  only weakly anticorrelated. Light curves can thus only give incomplete
  predictions of convective blueshift suppression. We must instead seek
  proxies that track the plage coverage on the visible stellar hemisphere
  directly. The chromospheric flux index R^' }_{HK} derived from the
  HARPS spectra performs poorly in this respect, possibly because of
  the differences in limb brightening/darkening in the chromosphere and
  photosphere. We also find that the activity-driven RV variations of the
  Sun are strongly correlated with its full-disc magnetic flux density,
  which may become a useful proxy for activity-related RV noise.

Title: VizieR Online Data Catalog: Lagoon Nebula M8 T tauri accretion
    rates (Kalari+, 2015)
Authors: Kalari, V. M.; Vink, J. S.; Drew, J. E.; Barentsen, G.;
   Drake, J. J.; Eisloffel, J.; Martin, E. L.; Parker, Q. A.; Unruh,
   Y. C.; Walton, N. A.; Wright, N. J.
Bibcode: 2016yCat..74531026K
Altcode:
  VPHAS+ imaging is obtained by the OmegaCAM CCD imager mounted on
  the 2.6m VLT Survey Telescope (VST) on Cerro Paranal, Chile. The
  imager captures a 1° square field of view at a resolution of
  0.21arcsec/pix. Each pointing is supplemented by at least one offset
  exposure to minimize CCD gaps. Imaging is carried out through broad-band
  ugri filters and a purpose-built Hα filter. The central wavelength and
  bandpass of the Hα filter are 6588 and 107Å, respectively. Exposure
  times are 150, 30, 25, 25, and 120s, respectively. VPHAS+ reaches a
  5σ depth at Hα=20.5-21.0mag and g=22.2-22.7mag. Practical constraints
  have meant that the blue (ug) and red (riHα) observations are carried
  out separately. An additional r observation is carried out with every
  blue observation to serve as a linking reference. <P />(2 data files).

Title: EUV-driven ionospheres and electron transport on extrasolar
    giant planets orbiting active stars
Authors: Chadney, J. M.; Galand, M.; Koskinen, T. T.; Miller, S.;
   Sanz-Forcada, J.; Unruh, Y. C.; Yelle, R. V.
Bibcode: 2016A&A...587A..87C
Altcode: 2016arXiv160103216C
  The composition and structure of the upper atmospheres of extrasolar
  giant planets (EGPs) are affected by the high-energy spectrum of their
  host stars from soft X-rays to the extreme ultraviolet (EUV). This
  emission depends on the activity level of the star, which is primarily
  determined by its age. In this study, we focus upon EGPs orbiting K-
  and M-dwarf stars of different ages - <ASTROBJ>ɛ Eridani</ASTROBJ>,
  <ASTROBJ>AD Leonis</ASTROBJ>, <ASTROBJ>AU Microscopii</ASTROBJ>
  - and the <ASTROBJ>Sun</ASTROBJ>. X-ray and EUV (XUV) spectra for
  these stars are constructed using a coronal model. These spectra
  are used to drive both a thermospheric model and an ionospheric
  model, providing densities of neutral and ion species. Ionisation -
  as a result of stellar radiation deposition - is included through
  photo-ionisation and electron-impact processes. The former is calculated
  by solving the Lambert-Beer law, while the latter is calculated from a
  supra-thermal electron transport model. We find that EGP ionospheres
  at all orbital distances considered (0.1-1 AU) and around all stars
  selected are dominated by the long-lived H<SUP>+</SUP> ion. In
  addition, planets with upper atmospheres where H<SUB>2</SUB> is not
  substantially dissociated (at large orbital distances) have a layer
  in which H<SUB>3</SUB><SUP>+</SUP> is the major ion at the base of
  the ionosphere. For fast-rotating planets, densities of short-lived
  H<SUB>3</SUB><SUP>+</SUP> undergo significant diurnal variations,
  with the maximum value being driven by the stellar X-ray flux. In
  contrast, densities of longer-lived H<SUP>+</SUP> show very little
  day/night variability and the magnitude is driven by the level of
  stellar EUV flux. The H<SUB>3</SUB><SUP>+</SUP> peak in EGPs with
  upper atmospheres where H<SUB>2</SUB> is dissociated (orbiting close to
  their star) under strong stellar illumination is pushed to altitudes
  below the homopause, where this ion is likely to be destroyed through
  reactions with heavy species (e.g. hydrocarbons, water). The inclusion
  of secondary ionisation processes produces significantly enhanced ion
  and electron densities at altitudes below the main EUV ionisation peak,
  as compared to models that do not include electron-impact ionisation. We
  estimate infrared emissions from H<SUB>3</SUB><SUP>+</SUP>, and while,
  in an H/H<SUB>2</SUB>/He atmosphere, these are larger from planets
  orbiting close to more active stars, they still appear too low to be
  detected with current observatories.

Title: Classical T Tauri stars with VPHAS+ - I. H α and u-band
    accretion rates in the Lagoon Nebula M8
Authors: Kalari, V. M.; Vink, J. S.; Drew, J. E.; Barentsen, G.;
   Drake, J. J.; Eislöffel, J.; Martín, E. L.; Parker, Q. A.; Unruh,
   Y. C.; Walton, N. A.; Wright, N. J.
Bibcode: 2015MNRAS.453.1026K
Altcode: 2015arXiv150706786K
  We estimate the accretion rates of 235 Classical T Tauri star (CTTS)
  candidates in the Lagoon Nebula using ugri H α photometry from the VST
  Photometric H α survey+. Our sample consists of stars displaying H α
  excess, the intensity of which is used to derive accretion rates. For a
  subset of 87 stars, the intensity of the u-band excess is also used to
  estimate accretion rates. We find the mean variation in accretion rates
  measured using H α and u-band intensities to be ∼0.17 dex, agreeing
  with previous estimates (0.04-0.4 dex) but for a much larger sample. The
  spatial distribution of CTTS align with the location of protostars and
  molecular gas suggesting that they retain an imprint of the natal gas
  fragmentation process. Strong accretors are concentrated spatially,
  while weak accretors are more distributed. Our results do not support
  the sequential star-forming processes suggested in the literature.

Title: Modelling the ionosphere of gas-giant exoplanets irradiated
    by low-mass stars
Authors: Chadney, J.; Galand, M.; Unruh, Y.; Koskinen, T.;
   Sanz-Forcada, J.
Bibcode: 2015EPSC...10..307C
Altcode:
  The composition and structure of the upper atmosphere of Extrasolar
  Giant Planets (EGPs) are affected by the high-energy spectrum of
  the host star from soft X-rays to Extreme UltraViolet (EUV) (0.1-10
  nm). This emission depends on the activity level of the star, which is
  primarily determined by its age [1]. In this study, we focus upon EGPs
  orbiting K- and M-dwarf stars of different ages. XUV spectra for these
  stars are constructed using a coronal model [2]. These spectra are used
  to drive both a thermospheric [3] and an ionospheric model, providing
  densities of neutral and ion species. Ionisation is included through
  photo-ionisation and electronimpact processes. The former is calculated
  by solving the Lambert-Beer law, while the latter is calculated from a
  supra-thermal electron transport model [4]. Planets orbiting far from
  the star are found to undergo Jeans escape, whereas close-orbiting
  planets undergo hydrodynamic escape. The critical orbital distance of
  transition between the two regimes is dependent on the level of stellar
  activity. We also find that EGP ionospheres at all orbital distances
  considered (0.1-1 AU) and around all stars selected (eps Eri, AD Leo,
  AU Mic) are dominated by the long-lived H+ ion. In addition, planets
  in the Jeans escape regime also have a layer in which H3 + is the major
  ion at the base of the ionosphere. For fast-rotating planets, densities
  of short-lived H3 + undergo significant diurnal variations, their
  peak value being determined by the stellar X-ray flux. In contrast,
  densities of longer-lived H+ show very little day/night variability and
  their value is determined by the level of stellar EUV flux. The H3 +
  peak in EGPs in the hydrodynamic escape regime under strong stellar
  illumination is pushed to altitudes below the homopause, where this
  ion is likely to be destroyed through reactions with heavy species
  (e.g., hydrocarbons, water). Infrared emissions from H3 + shall also
  be discussed, as well as the impact of stellar variability.

Title: UV solar irradiance in observations and the NRLSSI and
    SATIRE-S models
Authors: Yeo, K. L.; Ball, W. T.; Krivova, N. A.; Solanki, S. K.;
   Unruh, Y. C.; Morrill, J.
Bibcode: 2015JGRA..120.6055Y
Altcode: 2015arXiv150701224Y
  Total solar irradiance and UV spectral solar irradiance has been
  monitored since 1978 through a succession of space missions. This is
  accompanied by the development of models aimed at replicating solar
  irradiance by relating the variability to solar magnetic activity. The
  Naval Research Laboratory Solar Spectral Irradiance (NRLSSI) and
  Spectral And Total Irradiance REconstruction for the Satellite era
  (SATIRE-S) models provide the most comprehensive reconstructions of
  total and spectral solar irradiance over the period of satellite
  observation currently available. There is persistent controversy
  between the various measurements and models in terms of the wavelength
  dependence of the variation over the solar cycle, with repercussions on
  our understanding of the influence of UV solar irradiance variability
  on the stratosphere. We review the measurement and modeling of UV solar
  irradiance variability over the period of satellite observation. The
  SATIRE-S reconstruction is consistent with spectral solar irradiance
  observations where they are reliable. It is also supported by an
  independent, empirical reconstruction of UV spectral solar irradiance
  based on Upper Atmosphere Research Satellite/Solar Ultraviolet Spectral
  Irradiance Monitor measurements from an earlier study. The weaker
  solar cycle variability produced by NRLSSI between 300 and 400 nm is
  not evident in any available record. We show that although the method
  employed to construct NRLSSI is principally sound, reconstructed solar
  cycle variability is detrimentally affected by the uncertainty in the
  SSI observations it draws upon in the derivation. Based on our findings,
  we recommend, when choosing between the two models, the use of SATIRE-S
  for climate studies.

Title: New OB star candidates in the Carina Arm around Westerlund
    2 from VPHAS+
Authors: Mohr-Smith, M.; Drew, J. E.; Barentsen, G.; Wright, N. J.;
   Napiwotzki, R.; Corradi, R. L. M.; Eislöffel, J.; Groot, P.; Kalari,
   V.; Parker, Q. A.; Raddi, R.; Sale, S. E.; Unruh, Y. C.; Vink, J. S.;
   Wesson, R.
Bibcode: 2015MNRAS.450.3855M
Altcode: 2015arXiv150404342M
  O and early B stars are at the apex of galactic ecology, but in the
  Milky Way, only a minority of them may yet have been identified. We
  present the results of a pilot study to select and parametrize OB star
  candidates in the Southern Galactic plane, down to a limiting magnitude
  of g = 20. A 2 deg<SUP>2</SUP> field capturing the Carina Arm around the
  young massive star cluster, Westerlund 2, is examined. The confirmed OB
  stars in this cluster are used to validate our identification method,
  based on selection from the (u - g, g - r) diagram for the region. Our
  Markov Chain Monte Carlo fitting method combines VPHAS+ u, g, r, i with
  published J, H, K photometry in order to derive posterior probability
  distributions of the stellar parameters log (T<SUB>eff</SUB>) and
  distance modulus, together with the reddening parameters A<SUB>0</SUB>
  and R<SUB>V</SUB>. The stellar parameters are sufficient to confirm OB
  status while the reddening parameters are determined to a precision of
  σ(A<SUB>0</SUB>) ∼ 0.09 and σ(R<SUB>V</SUB>) ∼ 0.08. There are 489
  objects that fit well as new OB candidates, earlier than ∼B2. This
  total includes 74 probable massive O stars, 5 likely blue supergiants
  and 32 reddened subdwarfs. This increases the number of previously
  known and candidate OB stars in the region by nearly a factor of
  10. Most of the new objects are likely to be at distances between 3
  and 6 kpc. We have confirmed the results of previous studies that,
  at these longer distances, these sight lines require non-standard
  reddening laws with 3.5 &lt; R<SUB>V</SUB> &lt; 4.

Title: VizieR Online Data Catalog: VPHAS+ survey synthetic colours
    (Drew+, 2014)
Authors: Drew, J. E.; Gonzalez-Solares, E.; Greimel, R.; Irwin, M. J.;
   Kupcu Yoldas, A.; Lewis, J.; Barentsen, G.; Eisloffel, J.; Farnhill,
   H. J.; Martin, W. E.; Walsh, J. R.; Walton, N. A.; Mohr-Smith, M.;
   Raddi, R.; Sale, S. E.; Wright, N. J.; Groot, P.; Barlow, M. J.;
   Corradi, R. L. M.; Drake, J. J.; Fabregat, J.; Frew, D. J.; Gansicke,
   B. T.; Knigge, C.; Mampaso, A.; Morris, R. A. H.; Naylor, T.; Parker,
   Q. A.; Phillipps, S.; Ruhland, C.; Steeghs, D.; Unruh, Y. C.; Vink,
   J. S.; Wesson, R.; Zijlstra, A. A.
Bibcode: 2015yCat..74402036D
Altcode:
  Synthetic colours for main sequence stars, computed as described in
  Section 4 from model atmospheres, are here tabulated in full for three
  representative reddening laws (R<SUB>V</SUB> = 2.5, 3.1 and 3.8) and a
  range of reddenings (A0 = 0, 2, 4, 6, 8, 10). The form of the reddening
  laws used is due to Fitzpatrick &amp; Massa (2007ApJ...663..320F,
  Cat. J/ApJ/663/320). When using the blue-filter tables, it should be
  borne in mind that beyond g-r~3, the red leak in the u filter signif-
  icantly alters u-g. In this domain we expect the synthetic colours
  to progressively become less reliable as they increas- ingly depend
  on hard-to-measure very low levels of red trans- mission. Objects
  that appear to have these extreme, peculiar colours are likely to be
  reddened red giants or supergiants, since reddened K-M main sequence
  stars are too faint to be detected in VPHAS+ exposures. Beyond g-r~3.5
  these table entries are italicised. Two further tables of synthetic
  colours are included for K-M giants that have been computed using
  P98 library spectra. Data are provided for the R<SUB>V</SUB>=3.1 mean
  Galactic law only, for the limited purposes of (a) giving an impres-
  sion of how these luminous red objects may contaminate (u-g, g-r)
  diagrams at redder (g-r) through u red leak (b) enabling comparisons
  with the M-giant spur commonly seen in (r-Hα, r-i) colour-colour
  diagrams. <P />(8 data files).

Title: XUV-driven mass loss from extrasolar giant planets orbiting
    active stars
Authors: Chadney, J. M.; Galand, M.; Unruh, Y. C.; Koskinen, T. T.;
   Sanz-Forcada, J.
Bibcode: 2015Icar..250..357C
Altcode: 2014arXiv1412.3380C
  Upper atmospheres of Hot Jupiters are subject to extreme radiation
  conditions that can result in rapid atmospheric escape. The composition
  and structure of the upper atmospheres of these planets are affected
  by the high-energy spectrum of the host star. This emission depends on
  stellar type and age, which are thus important factors in understanding
  the behaviour of exoplanetary atmospheres. In this study, we focus
  on Extrasolar Giant Planets (EPGs) orbiting K and M dwarf stars. XUV
  spectra for three different stars - ɛ Eridani, AD Leonis and AU
  Microscopii - are constructed using a coronal model. Neutral density
  and temperature profiles in the upper atmosphere of hypothetical
  EGPs orbiting these stars are then obtained from a fluid model,
  incorporating atmospheric chemistry and taking atmospheric escape into
  account. We find that a simple scaling based solely on the host star's
  X-ray emission gives large errors in mass loss rates from planetary
  atmospheres and so we have derived a new method to scale the EUV
  regions of the solar spectrum based upon stellar X-ray emission. This
  new method produces an outcome in terms of the planet's neutral upper
  atmosphere very similar to that obtained using a detailed coronal model
  of the host star. Our results indicate that in planets subjected to
  radiation from active stars, the transition from Jeans escape to a
  regime of hydrodynamic escape at the top of the atmosphere occurs at
  larger orbital distances than for planets around low activity stars
  (such as the Sun).

Title: The second data release of the INT Photometric Hα Survey of
    the Northern Galactic Plane (IPHAS DR2)
Authors: Barentsen, Geert; Farnhill, H. J.; Drew, J. E.;
   González-Solares, E. A.; Greimel, R.; Irwin, M. J.; Miszalski, B.;
   Ruhland, C.; Groot, P.; Mampaso, A.; Sale, S. E.; Henden, A. A.;
   Aungwerojwit, A.; Barlow, M. J.; Carter, P. J.; Corradi, R. L. M.;
   Drake, J. J.; Eislöffel, J.; Fabregat, J.; Gänsicke, B. T.; Gentile
   Fusillo, N. P.; Greiss, S.; Hales, A. S.; Hodgkin, S.; Huckvale, L.;
   Irwin, J.; King, R.; Knigge, C.; Kupfer, T.; Lagadec, E.; Lennon,
   D. J.; Lewis, J. R.; Mohr-Smith, M.; Morris, R. A. H.; Naylor, T.;
   Parker, Q. A.; Phillipps, S.; Pyrzas, S.; Raddi, R.; Roelofs, G. H. A.;
   Rodríguez-Gil, P.; Sabin, L.; Scaringi, S.; Steeghs, D.; Suso, J.;
   Tata, R.; Unruh, Y. C.; van Roestel, J.; Viironen, K.; Vink, J. S.;
   Walton, N. A.; Wright, N. J.; Zijlstra, A. A.
Bibcode: 2014MNRAS.444.3230B
Altcode: 2014arXiv1406.4862B
  The INT/WFC Photometric Hα Survey of the Northern Galactic Plane
  (IPHAS) is a 1800 deg<SUP>2</SUP> imaging survey covering Galactic
  latitudes |b| &lt; 5° and longitudes ℓ = 30°-215° in the r, i, and
  Hα filters using the Wide Field Camera (WFC) on the 2.5-m Isaac Newton
  Telescope (INT) in La Palma. We present the first quality-controlled
  and globally calibrated source catalogue derived from the survey,
  providing single-epoch photometry for 219 million unique sources
  across 92 per cent of the footprint. The observations were carried out
  between 2003 and 2012 at a median seeing of 1.1 arcsec (sampled at 0.33
  arcsec pixel<SUP>-1</SUP>) and to a mean 5σ depth of 21.2 (r), 20.0
  (i), and 20.3 (Hα) in the Vega magnitude system. We explain the data
  reduction and quality control procedures, describe and test the global
  re-calibration, and detail the construction of the new catalogue. We
  show that the new calibration is accurate to 0.03 mag (root mean square)
  and recommend a series of quality criteria to select accurate data from
  the catalogue. Finally, we demonstrate the ability of the catalogue's
  unique (r - Hα, r - i) diagram to (i) characterize stellar populations
  and extinction regimes towards different Galactic sightlines and (ii)
  select and quantify Hα emission-line objects. IPHAS is the first
  survey to offer comprehensive CCD photometry of point sources across
  the Galactic plane at visible wavelengths, providing the much-needed
  counterpart to recent infrared surveys.

Title: A New SATIRE-S Spectral Solar Irradiance Reconstruction for
    Solar Cycles 21-23 and Its Implications for Stratospheric Ozone*
Authors: Ball, William T.; Krivova, Natalie A.; Unruh, Yvonne C.;
   Haigh, Joanna D.; Solanki, Sami K.
Bibcode: 2014JAtS...71.4086B
Altcode: 2014arXiv1408.0365B
  We present a revised and extended total and spectral solar irradiance
  (SSI) reconstruction, which includes a wavelength-dependent uncertainty
  estimate, spanning the last three solar cycles using the SATIRE-S
  model. The SSI reconstruction covers wavelengths between 115 and
  160,000 nm and all dates between August 1974 and October 2009. This
  represents the first full-wavelength SATIRE-S reconstruction to
  cover the last three solar cycles without data gaps and with an
  uncertainty estimate. SATIRE-S is compared with the NRLSSI model and
  SORCE/SOLSTICE ultraviolet (UV) observations. SATIRE-S displays similar
  cycle behaviour to NRLSSI for wavelengths below 242 nm and almost twice
  the variability between 242 and 310 nm. During the decline of last
  solar cycle, between 2003 and 2008, SSI from SORCE/SOLSTICE version
  12 and 10 typically displays more than three times the variability of
  SATIRE-S between 200 and 300 nm. All three datasets are used to model
  changes in stratospheric ozone within a 2D atmospheric model for a
  decline from high solar activity to solar minimum. The different flux
  changes result in different modelled ozone trends. Using NRLSSI leads
  to a decline in mesospheric ozone, while SATIRE-S and SORCE/SOLSTICE
  result in an increase. Recent publications have highlighted increases
  in mesospheric ozone when considering version 10 SORCE/SOLSTICE
  irradiances. The recalibrated SORCE/SOLSTICE version 12 irradiances
  result in a much smaller mesospheric ozone response than when using
  version 10 and now similar in magnitude to SATIRE-S. This shows that
  current knowledge of variations in spectral irradiance is not sufficient
  to warrant robust conclusions concerning the impact of solar variability
  on the atmosphere and climate.

Title: Variability of Sun-like stars: reproducing observed photometric
    trends
Authors: Shapiro, A. I.; Solanki, S. K.; Krivova, N. A.; Schmutz,
   W. K.; Ball, W. T.; Knaack, R.; Rozanov, E. V.; Unruh, Y. C.
Bibcode: 2014A&A...569A..38S
Altcode: 2014arXiv1406.2383S
  Context. The Sun and stars with low magnetic activity levels become
  photometrically brighter when their activity increases. Magnetically
  more active stars display the opposite behavior and become fainter
  when their activity increases. <BR /> Aims: We reproduce the observed
  photometric trends in stellar variations with a model thattreats stars
  as hypothetical suns with coverage by magnetic features different from
  that of the Sun. <BR /> Methods: The model attributes the variability
  of stellar spectra to the imbalance between the contributions from
  different components of the solar atmosphere, such as dark starspots
  and bright faculae. A stellar spectrum is calculated from spectra
  of the individual components by weighting them with corresponding
  disk-area coverages. The latter are obtained by extrapolating
  the solar dependences of spot and facular disk-area coverages
  on chromospheric activity to stars with different levels of mean
  chromospheric activity. <BR /> Results: We find that the contribution
  by starspots to the variability increases faster with chromospheric
  activity than the facular contribution. This causes the transition from
  faculae-dominated variability and direct activity-brightness correlation
  to spot-dominated variability and inverse activity-brightness
  correlation with increasing chromospheric activity level. We show that
  the regime of the variability also depends on the angle between the
  stellar rotation axis and the line-of-sight and on the latitudinal
  distribution of active regions on the stellar surface. Our model
  can be used as a tool for extrapolating the observed photometric
  variability of the Sun to Sun-like stars at different activity levels,
  which makes a direct comparison between solar and stellar irradiance
  data possible. <P />Appendices are available in electronic form at <A
  href="http://www.aanda.org/10.1051/0004-6361/201323086/olm">http://www.aanda.org</A>

Title: VizieR Online Data Catalog: IPHAS DR2 Source Catalogue
    (Barentsen+, 2014)
Authors: Barentsen, G.; Farnhill, H. J.; Drew, J. E.; Gonzalez-Solares,
   E. A.; Greimel, R.; Irwin, M. J.; Miszalski, B.; Ruhland, C.; Groot,
   P.; Mampaso, A.; Sale, S. E.; Henden, A. A.; Aungwerojwit, A.; Barlow,
   M. J.; Carter, P. J.; Corradi, R. L. M.; Drake, J. J.; Eisloffel, J.;
   Fabregat, J.; Gansicke, B. T.; Gentile Fusillo, N. P.; Greiss, S.;
   Hales, A. S.; Hodgkin, S.; Huckvale, L.; Irwin, J.; King, R.; Knigge,
   C.; Kupfer, T.; Lagadec, E.; Lennon, D. J.; Lewis, J. R.; Mohr-Smith,
   M.; Morris, R. A. H.; Naylor, T.; Parker, Q. A.; Phillipps, S.;
   Pyrzas, S.; Raddi, R.; Roelofs, G. H. A.; Rodriguez-Gil, P.; Sabin,
   L.; Scaringi, S.; Steeghs, D.; Suso, J.; Tata, R.; Unruh, Y. C.;
   van Roestel, J.; Viironen, K.; Vink, J. S.; Walton, N. A.; Wright,
   N. J.; Zijlstra, A. A.
Bibcode: 2014yCat.2321....0B
Altcode:
  The INT/WFC Photometric H-Alpha Survey of the Northern Galactic Plane
  (IPHAS) is a 1860 deg<SUP>2</SUP> imaging survey of the Northern Milky
  Way at red visible wavelengths. It covers Galactic latitudes |b|&lt;5°
  and longitudes l=30 to 215° in the broad-band r, i and narrow-band
  H-alpha filters using the Wide Field Camera (WFC) on the 2.5-m Isaac
  Newton Telescope (INT) in La Palma. <P />IPHAS Data Release 2 (DR2) is
  the first quality-controlled and globally calibrated source catalogue
  derived from the survey, providing single-epoch photometry for 219
  million unique sources across 92% of the footprint. The observations
  were carried out between 2003 and 2012 at a median seeing of 1.1 arcsec
  (sampled at 0.33 arcsec/pixel) and to a mean 5-sigma depth of 21.2
  (r), 20.0 (i) and 20.3 (H-alpha). The photometric calibration is in
  the Vega magnitude system and carries an external precision of 0.03mag
  (root-mean-square error). <P />The catalogue includes all the sources
  which have been detected at a signal-to-noise ratio of 5 or better
  in at least one band. Many applications will require a combination
  of quality criteria to be applied to avoid faint stars or confused
  sources. The choice of quality criteria tensions completeness against
  reliability, and hence depends on the requirements of a project. To
  aid users, the data release paper (arXiv:1406.4862) recommends two sets
  of quality criteria, named "a10" and "a10point", which should satisfy
  most projects. As a minimum, the "a10" criteria select objects which
  have been detected at the minimum level of 10-sigma in all bands,
  without being saturated. Additional constraints are provided by the
  "a10point" criteria, which require objects to be point sources free
  of blending, unaffected by nearby bright stars, as well as being
  unsaturated &gt;10-sigma detections in all bands. Sources in both
  categories are flagged in the catalogue using the boolean columns a10
  and a10point. <P />Imaging and auxiliary data are available from the
  project website (www.iphas.org). <P />(1 data file).

Title: Planets and stellar activity: hide and seek in the CoRoT-7
    system
Authors: Haywood, R. D.; Collier Cameron, A.; Queloz, D.; Barros,
   S. C. C.; Deleuil, M.; Fares, R.; Gillon, M.; Lanza, A. F.; Lovis,
   C.; Moutou, C.; Pepe, F.; Pollacco, D.; Santerne, A.; Ségransan,
   D.; Unruh, Y. C.
Bibcode: 2014MNRAS.443.2517H
Altcode: 2014arXiv1407.1044H
  Since the discovery of the transiting super-Earth CoRoT-7b, several
  investigations have yielded different results for the number and masses
  of planets present in the system, mainly owing to the star's high level
  of activity. We re-observed CoRoT-7 in 2012 January with both HARPS and
  CoRoT, so that we now have the benefit of simultaneous radial-velocity
  and photometric data. This allows us to use the off-transit variations
  in the star's light curve to estimate the radial-velocity variations
  induced by the suppression of convective blueshift and the flux blocked
  by starspots. To account for activity-related effects in the radial
  velocities which do not have a photometric signature, we also include
  an additional activity term in the radial-velocity model, which we
  treat as a Gaussian process with the same covariance properties (and
  hence the same frequency structure) as the light curve. Our model
  was incorporated into a Monte Carlo Markov Chain in order to make
  a precise determination of the orbits of CoRoT-7b and CoRoT-7c. We
  measure the masses of planets b and c to be 4.73 ± 0.95 and 13.56
  ± 1.08 M<SUB>⊕</SUB>, respectively. The density of CoRoT-7b is
  (6.61 ± 1.72)(R<SUB>p</SUB>/1.58 R<SUB>⊕</SUB>)<SUP>-3</SUP> g
  cm<SUP>-3</SUP>, which is compatible with a rocky composition. We search
  for evidence of an additional planet d, identified by previous authors
  with a period close to 9 d. We are not able to confirm the existence
  of a planet with this orbital period, which is close to the second
  harmonic of the stellar rotation at ∼7.9 d. Using Bayesian model
  selection, we find that a model with two planets plus activity-induced
  variations is most favoured.

Title: The VST Photometric Hα Survey of the Southern Galactic Plane
    and Bulge (VPHAS+)
Authors: Drew, J. E.; Gonzalez-Solares, E.; Greimel, R.; Irwin,
   M. J.; Küpcü Yoldas, A.; Lewis, J.; Barentsen, G.; Eislöffel,
   J.; Farnhill, H. J.; Martin, W. E.; Walsh, J. R.; Walton, N. A.;
   Mohr-Smith, M.; Raddi, R.; Sale, S. E.; Wright, N. J.; Groot, P.;
   Barlow, M. J.; Corradi, R. L. M.; Drake, J. J.; Fabregat, J.; Frew,
   D. J.; Gänsicke, B. T.; Knigge, C.; Mampaso, A.; Morris, R. A. H.;
   Naylor, T.; Parker, Q. A.; Phillipps, S.; Ruhland, C.; Steeghs, D.;
   Unruh, Y. C.; Vink, J. S.; Wesson, R.; Zijlstra, A. A.
Bibcode: 2014MNRAS.440.2036D
Altcode: 2014arXiv1402.7024D; 2014MNRAS.tmp..599D; 2014MNRAS.tmp..608D
  The VST Photometric Hα Survey of the Southern Galactic Plane and Bulge
  (VPHAS+) is surveying the southern Milky Way in u, g, r, i and Hα
  at ∼1 arcsec angular resolution. Its footprint spans the Galactic
  latitude range -5<SUP>o</SUP> &lt; b &lt; +5° at all longitudes south
  of the celestial equator. Extensions around the Galactic Centre to
  Galactic latitudes ±10° bring in much of the Galactic bulge. This
  European Southern Observatory public survey, begun on 2011 December 28,
  reaches down to ∼20th magnitude (10σ) and will provide single-epoch
  digital optical photometry for ∼300 million stars. The observing
  strategy and data pipelining are described, and an appraisal of the
  segmented narrow-band Hα filter in use is presented. Using model
  atmospheres and library spectra, we compute main-sequence (u - g),
  (g - r), (r - i) and (r - Hα) stellar colours in the Vega system. We
  report on a preliminary validation of the photometry using test data
  obtained from two pointings overlapping the Sloan Digital Sky Survey. An
  example of the (u - g, g - r) and (r - Hα, r - i) diagrams for a full
  VPHAS+ survey field is given. Attention is drawn to the opportunities
  for studies of compact nebulae and nebular morphologies that arise
  from the image quality being achieved. The value of the u band as the
  means to identify planetary-nebula central stars is demonstrated by the
  discovery of the central star of NGC 2899 in survey data. Thanks to its
  excellent imaging performance, the VLT Survey Telescope (VST)/OmegaCam
  combination used by this survey is a perfect vehicle for automated
  searches for reddened early-type stars, and will allow the discovery
  and analysis of compact binaries, white dwarfs and transient sources.

Title: Disentangling planetary orbits from stellar activity in
    radial-velocity surveys
Authors: Haywood, R. D.; Collier Cameron, A.; Queloz, D.; Barros,
   S. C. C.; Deleuil, M.; Fares, R.; Gillon, M.; Hatzes, A.; Lanza,
   A. F.; Lovis, C.; Moutou, C.; Pepe, F.; Pollacco, D.; Santerne, A.;
   Ségransan, D.; Unruh, Y.
Bibcode: 2014IJAsB..13..155H
Altcode:
  The majority of extra-solar planets have been discovered (or confirmed
  after follow-up) through radial-velocity (RV) surveys. Using
  ground-based spectrographs such as High Accuracy Radial Velocity
  Planetary Search (HARPS) and HARPS-North, it is now possible to detect
  planets that are only a few times the mass of the Earth. However, the
  presence of dark spots on the stellar surface produces RV signals that
  are very similar in amplitude to those caused by orbiting low-mass
  planets. Disentangling these signals has thus become the biggest
  challenge in the detection of Earth-mass planets using RV surveys. To do
  so, we use the star's lightcurve to model the RV variations produced
  by spots. Here we present this method and show the results of its
  application to CoRoT-7.

Title: Modelling of Hot Jupiter thermospheres and ionospheres under
    irradiation from active stars
Authors: Chadney, J.; Galand, M.; Unruh, Y.; Koskinen, T.;
   Sanz-Forcada, J.
Bibcode: 2014EPSC....9..579C
Altcode:
  Upper atmospheres of Hot Jupiters are subject to extreme radiation
  conditions that can result in atmospheric escape. The composition
  and structure of the thermosphere and ionosphere of these planets are
  affected by the high-energy spectrum of the host star. This emission
  depends on stellar type and age, which are thus important factors in
  understanding the behaviour of exoplanetary atmospheres. In this study,
  we focus on Hot Jupiter planets orbiting K and M dwarf stars. As an
  example, XUV spectra for three different stars - ɛ Eridani, AD Leonis
  and AU Microscopii - are constructed using a coronal model. Neutral
  density and temperature profiles in the thermosphere of hypothetical,
  Hot Jupiters orbiting these stars are then obtained from a fluid
  model of the upper atmosphere, incorporating atmospheric chemistry
  and taking atmospheric escape into account. Using these models of both
  the host star and the planetary atmosphere, we have derived a method
  to scale the X-ray and EUV regions of the solar spectrum to produce
  a very similar outcome in terms of the planet's neutral thermosphere
  as using a detailed coronal model of the host star. We also calculate
  ion production rates and densities in the ionospheres of such planets,
  considering ionisation through both photo-ionisation and electronimpact
  processes. We find that in planets subjected to radiation from more
  active stars, the transition to a regime of hydrodynamic escape from
  the top of the atmosphere occurs at larger orbital distances. A greater
  X-ray to EUV flux ratio in these stars compared with the solar case
  also produces ionospheres that extend to lower altitudes and are
  significantly more pronounced.

Title: Planets and Stellar Activity: Hide and Seek in the CoRoT-7
    system
Authors: Haywood, R. D.; Cameron, A. C.; Queloz, D.; Barros, S. C. C.;
   Deleuil, M.; Fares, R.; Gillon, M.; Hatzes, A.; Lanza, A. F.; Lovis,
   C.; Moutou, C.; Pepe, F.; Pollacco, D.; Santerne, A.; Ségransan,
   D.; Unruh, Y.
Bibcode: 2014IAUS..299..237H
Altcode:
  Since the discovery of the transiting Super-Earth CoRoT-7b, several
  investigations have been made of the number and precise masses of
  planets present in the system, but they all yield different results,
  owing to the star's high level of activity. Radial velocity (RV)
  variations induced by stellar activity therefore need to be modelled
  and removed to allow a reliable detection of all planets in the
  system. We re-observed CoRoT-7 in January 2012 with both HARPS and
  the CoRoT satellite, so that we now have the benefit of simultaneous
  RV and photometric data. We fitted the off-transit variations in
  the CoRoT lightcurve using a harmonic decomposition similar to that
  implemented in Queloz et al. (2009). This fit was then used to model
  the stellar RV contribution, according to the methods described by
  Aigrain et al. (2011). This model was incorporated into a Monte Carlo
  Markov Chain in order to make a precise determination of the orbits
  of CoRoT-7b and CoRoT-7c. We also assess the evidence for the presence
  of one or two additional planetary companions.

Title: VST Photometric H-alpha Survey of the Southern Galactic Plane
    and Bulge (VPHAS+)
Authors: Drew, J. E.; Barentsen, G.; Fabregat, J.; Farnhill, H.;
   Mohr-Smith, M.; Wright, N. J.; Gonzalez-Solares, E.; Irwin, M. J.;
   Lewis, J.; Yoldas, A. K.; Greimel, R.; Eislöffel, J.; Groot, P.;
   Barlow, M. J.; Corradi, R.; Gänsicke, B. T.; Knigge, C.; Mampaso,
   A.; Morris, R.; Naylor, T.; Parker, Q. A.; Raddi, R.; Sale, S. E.;
   Steeghs, D.; Unruh, Y. C.; Vink, J. S.; Walsh, J. R.; Walton, N. A.;
   Wesson, R.; Zijlstra, A.
Bibcode: 2013Msngr.154...41D
Altcode:
  The VST Photometric H-alpha survey of the Southern Galactic Plane and
  Bulge (VPHAS+) is collecting single-epoch Sloan u, g, r, i and H-alpha
  narrowband photometry, at arcsecond resolution, down to point-source
  (Vega) magnitudes of ~ 21. The survey footprint encloses the entire
  southern Galactic Plane within the Galactic latitude range -5° &lt;
  b &lt; +5°, expanding to b = ±10° in the Galactic Bulge. This
  brief description of VPHAS+ includes sample data and examples of early
  science validation.

Title: Hot-Jupiter ionospheres irradiated by low-mass stars
Authors: Chadney, J.; Galand, M.; Unruh, Y.; Koskinen, T.;
   Sanz-Forcada, J.
Bibcode: 2013EPSC....8..800C
Altcode:
  We present a modelling study of the upper atmospheres of extra-solar
  planets, focussing on the influence of different stellar radiation
  spectra on the composition and structure of the ionosphere around
  a gas-giant planet. In particular, we concentrate on hot-Jupiter
  planets orbiting low mass stars, of K and M type. Compared to a solar
  type star, the XUV radiation of these stars is extremely variable and
  they have a much higher XUV-to-bolometric-flux ratio than similarly
  aged solar type stars - greatly affecting the planetary ionospheres
  they irradiate. In this work, XUV spectra for the different stars
  selected are constructed using a combination of spectral data from
  various space telescopes, as well as coronal models of the stars. Ion
  production rates and densities are then calculated for a given H2/H/He
  background atmosphere, taking into account ionisation through both
  primary and secondary processes. Additionally, the effect of orbital
  separation on ionospheric composition is examined. Results show that
  in atmospheres subjected to radiation from active M-dwarf stars,
  ion production is boosted in the lower ionosphere, which is also the
  region most affected by secondary ionisation processes.

Title: Studying the Sun's radial velocity jitter to improve low-mass
    exoplanet detections
Authors: Haywood, R. D.; Cameron, A. C.; Queloz, D.; Fares, R.; Llama,
   J.; Deleuil, M.; Gillon, M.; Hatzes, A.; Lanza, A. F.; Lovis, C.;
   Moutou, C.; Pepe, F.; Pollaco, D.; Ségransan, D.; Unruh, Y.
Bibcode: 2013EPSC....8..215H
Altcode:
  One of the most common methods used to discover extra-solar planets is
  to monitor a star's radial velocity (RV) in order to detect the reflex
  orbital motion caused by one or more planets orbiting the star. When
  looking for "small" planets (Neptune or Earth mass), the RV signals
  induced by these planets are entangled with the jitter arising from
  the star's magnetic activity. The Sun's activity is well known and it
  is possible to remove all RV components induced by all other bodies of
  the solar system. We have obtained its activity-driven RV variations
  over two solar rotations using HARPS by observing sunlight reflected off
  the bright asteroid Vesta. We aim to model the solar RV jitter in terms
  of the continuum lightcurve, the chromospheric Ca II H&amp;K emission,
  and the line-profile distortions produced by spots drifting across the
  face of the Sun. By using the "ground truth" of solar observations
  in this way, we will identify photometric and spectroscopic proxies
  that will make it possible to model and remove the stellar activity
  RV contribution from exoplanet RV curves.

Title: A Collaborative FP7 Effort towards the First European
    Comprehensive SOLar Irradiance Data Exploitation (SOLID)
Authors: Haberreiter, Margit; Dasi, Maria; Delouille, Veronique; Del
   Zanna, Giulio; Dudok de Wit, Thierry; Ermolli, Ilaria; Kretzschmar,
   Matthieu; Krivova, Natalie; Mason, Helen; Qahwaji, Rami; Schmutz,
   Werner; Solanki, Sami; Thuillier, Gerard; Tourpali, Kleareti; Unruh,
   Yvonne; Verbeeck, Cis; Weber, Mark; Woods, Tom
Bibcode: 2013EGUGA..1513079H
Altcode:
  Variations of solar irradiance are the most important natural factor
  in the terrestrial climate and as such, the time dependent spectral
  solar irradiance is a crucial input to any climate modelling. There
  have been previous efforts to compile solar irradiance but it is
  still uncertain by how much the spectral and total solar irradiance
  changed on yearly, decadal and longer time scales. Observations of
  irradiance data exist in numerous disperse data sets. Therefore, it
  is important to bring together the European expertise in the field
  to analyse and merge the complete set of European irradiance data,
  complemented by archive data that include data from non-European
  missions. We report on the initiation of a collaborative effort to unify
  representatives from all European solar space experiments and European
  teams specialized in multi-wavelength solar image processing. It is
  intended to include the European groups involved in irradiance modelling
  and reconstruction. They will work with two different state of the art
  approaches to produce reconstructed spectral and total solar irradiance
  data as a function of time. These results will be used to bridge
  gaps in time and wavelength coverage of the observational data. This
  will allow the proposing SOLID team to reduce the uncertainties in
  the irradiance time series - an important requirement by the climate
  community - and to provide uniform data sets of modelled and observed
  solar irradiance data from the beginning of the space era to the
  present including proper error and uncertainty estimates. Climate
  research needs these data sets and therefore, the primary benefit
  is for the climate community, but the stellar community, planetary,
  lunar, and ionospheric researchers are also interested in having at
  their disposition incident radiation of the Sun. The proposing team
  plans to realize a wide international synergy in solar physics from
  7 European countries, and collaborators from the US, complemented by
  representatives from the climate community, who will accompany their
  research work with wide dissemination activities.

Title: Modeling the variability of Sun-like stars
Authors: Shapiro, Alexander; Knaack, Reto; Krivova, Natalie; Schmutz,
   Werner; Solanki, Sami; Unruh, Yvonne
Bibcode: 2013EGUGA..15.9981S
Altcode:
  We present a model which attributes the variability of the stellar
  radiative energy flux to the imbalance between the contributions from
  dark starspots and bright faculae. The stellar radiative energy flux
  variations are modeled from the individual component's spectra, by
  weighting them with corresponding filling factors. The filling factors
  are deduced by extrapolating the sunspot and facular filling factors
  dependencies on solar CaII S-index to stars with different levels
  of the chromospheric activity. Our approach allows us to model the
  stellar photometric variability vs. activity dependency and reproduce
  the transition from spot-dominated to facula-dominated regimes of
  variability. We show how the effect of inclination (arising due to the
  random position of the Earth-bound observer relative to the directions
  of stellar rotational axis) can affect these dependencies and present
  the modeling of the individual stellar photometric light curves.

Title: Recent variability of the solar spectral irradiance and its
    impact on climate modelling
Authors: Ermolli, I.; Matthes, K.; Dudok de Wit, T.; Krivova,
   N. A.; Tourpali, K.; Weber, M.; Unruh, Y. C.; Gray, L.; Langematz,
   U.; Pilewskie, P.; Rozanov, E.; Schmutz, W.; Shapiro, A.; Solanki,
   S. K.; Woods, T. N.
Bibcode: 2013ACP....13.3945E
Altcode: 2012ACPD...1224557E; 2013arXiv1303.5577E
  The lack of long and reliable time series of solar spectral irradiance
  (SSI) measurements makes an accurate quantification of solar
  contributions to recent climate change difficult. Whereas earlier SSI
  observations and models provided a qualitatively consistent picture of
  the SSI variability, recent measurements by the SORCE (SOlar Radiation
  and Climate Experiment) satellite suggest a significantly stronger
  variability in the ultraviolet (UV) spectral range and changes in the
  visible and near-infrared (NIR) bands in anti-phase with the solar
  cycle. A number of recent chemistry-climate model (CCM) simulations
  have shown that this might have significant implications on the
  Earth's atmosphere. Motivated by these results, we summarize here
  our current knowledge of SSI variability and its impact on Earth's
  climate. <BR /><BR /> We present a detailed overview of existing SSI
  measurements and provide thorough comparison of models available to
  date. SSI changes influence the Earth's atmosphere, both directly,
  through changes in shortwave (SW) heating and therefore, temperature
  and ozone distributions in the stratosphere, and indirectly, through
  dynamical feedbacks. We investigate these direct and indirect effects
  using several state-of-the art CCM simulations forced with measured
  and modelled SSI changes. A unique asset of this study is the use
  of a common comprehensive approach for an issue that is usually
  addressed separately by different communities. <BR /><BR /> We show
  that the SORCE measurements are difficult to reconcile with earlier
  observations and with SSI models. Of the five SSI models discussed
  here, specifically NRLSSI (Naval Research Laboratory Solar Spectral
  Irradiance), SATIRE-S (Spectral And Total Irradiance REconstructions
  for the Satellite era), COSI (COde for Solar Irradiance), SRPM (Solar
  Radiation Physical Modelling), and OAR (Osservatorio Astronomico di
  Roma), only one shows a behaviour of the UV and visible irradiance
  qualitatively resembling that of the recent SORCE measurements. However,
  the integral of the SSI computed with this model over the entire
  spectral range does not reproduce the measured cyclical changes of the
  total solar irradiance, which is an essential requisite for realistic
  evaluations of solar effects on the Earth's climate in CCMs. <BR /><BR
  /> We show that within the range provided by the recent SSI observations
  and semi-empirical models discussed here, the NRLSSI model and SORCE
  observations represent the lower and upper limits in the magnitude
  of the SSI solar cycle variation. <BR /><BR /> The results of the
  CCM simulations, forced with the SSI solar cycle variations estimated
  from the NRLSSI model and from SORCE measurements, show that the direct
  solar response in the stratosphere is larger for the SORCE than for the
  NRLSSI data. Correspondingly, larger UV forcing also leads to a larger
  surface response. <BR /><BR /> Finally, we discuss the reliability
  of the available data and we propose additional coordinated work,
  first to build composite SSI data sets out of scattered observations
  and to refine current SSI models, and second, to run coordinated
  CCM experiments.

Title: Solar and stellar spectral variability
Authors: Unruh, Yvonne; Ball, William
Bibcode: 2013EGUGA..15.8414U
Altcode:
  Measurements of the changes in the solar spectral irradiance are
  available for three solar cycles and there is a good understanding
  of the irradiance changes on time scales ranging from a day to a few
  years. Observing longer-term changes (tens of years and longer) is more
  difficult, and there is much uncertainty regarding the Sun's long-term
  behaviour. Stellar comparisons are often used to explore a wider range
  of activity regimes and to estimate past and future solar variability
  levels. At the same time, we want to find out how different the solar
  example is and whether we can use it as a paradigm when finding and
  characterising exoplanets around cool stars. We will discuss some of
  the challenges that we encounter when comparing solar and stellar
  variability, such as, e.g., the spread of stellar inclinations and
  effective temperatures, and uncertainties in the relative area coverages
  and contrasts of dark and bright features. Considering different levels
  of spot and facular coverage for a range of effective temperatures,
  we investigate the expected spectral variability and compare it to
  observed solar and stellar variability.

Title: Solar irradiance variability
Authors: Solanki, S. K.; Unruh, Y. C.
Bibcode: 2013AN....334..145S
Altcode: 2013csss...17..145S; 2012arXiv1210.5911S
  The Sun has long been considered a constant star, to the extent
  that its total irradiance was termed the solar constant. It required
  radiometers in space to detect the small variations in solar irradiance
  on timescales of the solar rotation and the solar cycle. A part of
  the difficulty is that there are no other constant natural daytime
  sources to which the Sun's brightness can be compared. The discovery
  of solar irradiance variability rekindled a long-running discussion on
  how strongly the Sun affects our climate. A non-negligible influence is
  suggested by correlation studies between solar variability and climate
  indicators. The mechanism for solar irradiance variations that fits
  the observations best is that magnetic features at the solar surface,
  i.e. sunspots, faculae and the magnetic network, are responsible for
  almost all variations (although on short timescales convection and
  p-mode oscillations also contribute). In spite of significant progress
  important questions are still open. Thus there is a debate on how
  strongly irradiance varies on timescales of centuries (i.e. how much
  darker the Sun was during the Maunder minimum than it is today). It is
  also not clear how the solar spectrum changes over the solar cycle. Both
  these questions are of fundamental importance for working out just how
  strongly the Sun influences our climate. Another interesting question
  is how solar irradiance variability compares with that of other cool
  dwarfs, particularly now that observations from space are available
  also for stars.

Title: Ionisation of gas-giant type exoplanetary atmospheres under
    stellar radiation
Authors: Chadney, J.; Galand, M.; Unruh, Y.; Koskinen, T.
Bibcode: 2012epsc.conf..474C
Altcode: 2012espc.conf..474C
  Characterising extra-solar planetary atmospheres is the new frontier
  in exoplanetary research. Future space-based missions will provide
  consistent and stable measurements of star systems with known transiting
  exoplanets. These missions, that are currently at selection stage,
  are ESA's Exoplanet Characterisation Observatory (EChO) and NASA's Fast
  INfrared Exoplanet Spectroscopy Survey Explorer (FINESSE). Once up and
  running, they will deliver high stability, long duration observations
  in the visible to midinfrared. In the meantime, modelling studies of
  the atmospheres of extra-solar planets, such as the one undertaken
  in this work, will be useful to help plan the observational process
  and provide insight into the data analysis and interpretation, after
  the missions are launched. The purpose of this work is to study the
  influence of differing stellar radiation profiles on the composition and
  structure of an ionosphere around a typical gas-giant planet. Particular
  interest is focused upon M and K-type dwarf stars. Typical XUV spectra
  for the different star types are constructed by combining data from
  various satellites. Unobserved parts of the spectrum are filled
  using a combination of extrapolation and results from a correlation
  study of the solar spectrum. The constructed spectra are then used
  to calculate ion densities, produced through photo-ionisation, in a
  H2/H/He atmosphere, considering the neutral atmosphere as a constant
  background. Preliminary results show that in planets irradiated
  by K-type stars, photo-ionisation production rates are remarkably
  similar to those in planets orbiting Sun-like stars. The case of
  atmospheres subjected to radiation from flaring Mstars is altogether
  more interesting: an extension of the production rate peak towards
  lower altitudes is predicted.

Title: Solar Irradiance Models and Measurements: A Comparison in
    the 220-240 nm wavelength band
Authors: Unruh, Yvonne C.; Ball, Will T.; Krivova, Natalie A.
Bibcode: 2012SGeo...33..475U
Altcode: 2011arXiv1111.2068U; 2011SGeo..tmp..121U
  Solar irradiance models that assume solar irradiance variations
  to be due to changes in the solar surface magnetic flux have been
  successfully used to reconstruct total solar irradiance on rotational
  as well as cyclical and secular time scales. Modelling spectral solar
  irradiance is not yet as advanced, and also suffers from a lack of
  comparison data, in particular on solar cycle time scales. Here,
  we compare solar irradiance in the 220-240 nm band as modelled
  with SATIRE-S and measured by different instruments on the UARS
  and SORCE satellites. We find good agreement between the model and
  measurements on rotational time scales. The long-term trends, however,
  show significant differences. Both SORCE instruments, in particular,
  show a much steeper gradient over the decaying part of cycle 23 than
  the modelled irradiance or that measured by UARS/SUSIM.

Title: Reconstruction of total solar irradiance 1974-2009
Authors: Ball, W. T.; Unruh, Y. C.; Krivova, N. A.; Solanki, S.;
   Wenzler, T.; Mortlock, D. J.; Jaffe, A. H.
Bibcode: 2012A&A...541A..27B
Altcode: 2012arXiv1202.3554B
  Context. The study of variations in total solar irradiance (TSI)
  is important for understanding how the Sun affects the Earth's
  climate. <BR /> Aims: Full-disk continuum images and magnetograms are
  now available for three full solar cycles. We investigate how modelled
  TSI compares with direct observations by building a consistent modelled
  TSI dataset. The model, based only on changes in the photospheric
  magnetic flux can then be tested on rotational, cyclical and secular
  timescales. <BR /> Methods: We use Kitt Peak and SoHO/MDI continuum
  images and magnetograms in the SATIRE-S model to reconstruct TSI over
  cycles 21-23. To maximise independence from TSI composites, SORCE/TIM
  TSI data are used to fix the one free parameter of the model. We compare
  and combine the separate data sources for the model to estimate an
  uncertainty on the reconstruction and prevent any additional free
  parameters entering the model. <BR /> Results: The reconstruction
  supports the PMOD composite as being the best historical record of
  TSI observations, although on timescales of the solar rotation the
  IRMB composite provides somewhat better agreement. Further to this,
  the model is able to account for 92% of TSI variations from 1978
  to 2009 in the PMOD composite and over 96% during cycle 23. The
  reconstruction also displays an inter-cycle, secular decline of
  0.20<SUP>+0.12</SUP><SUB>-0.09</SUB> W m<SUP>-2</SUP> between cycle
  23 minima, in agreement with the PMOD composite. <BR /> Conclusions:
  SATIRE-S is able to recreate TSI observations on all timescales of a
  day and longer over 31 years from 1978. This is strong evidence that
  changes in photospheric magnetic flux alone are responsible for almost
  all solar irradiance variations over the last three solar cycles.

Title: Solar Irradiance Models and Measurements: A Comparison in
    the 220–240 nm wavelength band
Authors: Unruh, Yvonne C.; Ball, Will T.; Krivova, Natalie A.
Bibcode: 2012omee.book..143U
Altcode:
  No abstract at ADS

Title: The large-scale magnetic field and poleward mass accretion
    of the classical T Tauri star TW Hya
Authors: Donati, J. -F.; Gregory, S. G.; Alencar, S. H. P.; Bouvier,
   J.; Hussain, G.; Skelly, M.; Dougados, C.; Jardine, M. M.; Ménard,
   F.; Romanova, M. M.; Unruh, Y. C.
Bibcode: 2011MNRAS.417..472D
Altcode: 2011arXiv1106.4162D; 2011MNRAS.tmp.1284D
  We report here results of spectropolarimetric observations of the
  ≃8 Myr classical T Tauri star (cTTS) TW Hya carried out with
  ESPaDOnS at the Canada-France-Hawaii Telescope in the framework of
  the 'Magnetic Protostars and Planets' programme, and obtained at
  two different epochs (2008 March and 2010 March). Obvious Zeeman
  signatures are detected at all times, both in photospheric lines and
  in accretion-powered emission lines. Significant intrinsic variability
  and moderate rotational modulation are observed in both photospheric
  and accretion proxies. <P />Using tomographic imaging, we reconstruct
  maps of the large-scale field of the photospheric brightness and the
  accretion-powered emission at the surface of TW Hya at both epochs. We
  find that the magnetic topology is mostly poloidal and axisymmetric
  with respect to the rotation axis of the star and that the octupolar
  component of the large-scale field (2.5-2.8 kG at the pole) largely
  dominates the dipolar component. This large-scale field topology is
  characteristic of partly convective stars, supporting the conclusion
  (from evolutionary models) that TW Hya already hosts a radiative
  core. We also show that TW Hya features a high-latitude photospheric
  cool spot overlapping with the main magnetic pole (and producing the
  observed radial velocity fluctuations); this is also where accretion
  concentrates most of the time, although accretion at lower latitudes
  is found to occur episodically. <P />We propose that the relatively
  rapid rotation of TW Hya (with respect to AA Tau-like cTTSs) directly
  reflects the weakness of the large-scale dipole, no longer capable of
  magnetically disrupting the accretion disc up to the corotation radius
  (at which the Keplerian period equals the stellar rotation period). We
  therefore conclude that TW Hya is in a phase of rapid spin-up as its
  large-scale dipole field progressively vanishes.

Title: Solar irradiance variability: a six-year comparison between
    SORCE observations and the SATIRE model
Authors: Ball, W. T.; Unruh, Y. C.; Krivova, N. A.; Solanki, S.;
   Harder, J. W.
Bibcode: 2011A&A...530A..71B
Altcode: 2011arXiv1104.0885B
  <BR /> Aims: We investigate how well modeled solar irradiances agree
  with measurements from the SORCE satellite, both for total solar
  irradiance and broken down into spectral regions on timescales of
  several years. <BR /> Methods: We use the SATIRE model and compare
  modeled total solar irradiance (TSI) with TSI measurements over the
  period 25 February 2003 to 1 November 2009. Spectral solar irradiance
  over 200-1630 nm is compared with the SIM instrument on SORCE over
  the period 21 April 2004 to 1 November 2009. We discuss the overall
  change in flux and the rotational and long-term trends during this
  period of decline from moderate activity to the recent solar minimum
  in ~10 nm bands and for three spectral regions of significant interest:
  the UV integrated over 200-300 nm, the visible over 400-691 nm and the
  IR between 972-1630 nm. <BR /> Results: The model captures 97% of the
  observed TSI variation. This is on the order at which TSI detectors
  agree with each other during the period considered. In the spectral
  comparison, rotational variability is well reproduced, especially
  between 400 and 1200 nm. The magnitude of change in the long-term
  trends is many times larger in SIM at almost all wavelengths while
  trends in SIM oppose SATIRE in the visible between 500 and 700 nm and
  again between 1000 and 1200 nm. We discuss the remaining issues with
  both SIM data and the identified limits of the model, particularly
  with the way facular contributions are dealt with, the limit of flux
  identification in MDI magnetograms during solar minimum and the model
  atmospheres in the IR employed by SATIRE. However, it is unlikely that
  improvements in these areas will significantly enhance the agreement
  in the long-term trends. This disagreement implies that some mechanism
  other than surface magnetism is causing SSI variations, in particular
  between 2004 and 2006, if the SIM data are correct. Since SATIRE
  was able to reproduce UV irradiance between 1991 and 2002 from UARS,
  either the solar mechanism for SSI variation fundamentally changed
  around the peak of cycle 23, or there is an inconsistency between UARS
  and SORCE UV measurements. We favour the second explanation.

Title: Intensity contrast from MHD simulations and HINODE observations
Authors: Afram, N.; Unruh, Y. C.; Solanki, S. K.; Schüssler, M.;
   Lagg, A.; Vögler, A.
Bibcode: 2011A&A...526A.120A
Altcode: 2010arXiv1011.6102A
  Context. Changes in the solar surface area, which is covered by
  small-scale magnetic elements, are thought to cause long-term changes
  in the solar spectral irradiance, which are important for determining
  the impact on Earth's climate. <BR /> Aims: To study the effect of
  small-scale magnetic elements on the total and spectral irradiance,
  we derive their contrasts from 3-D MHD simulations of the solar
  atmosphere. These calculations are necessary because measurements of
  small-scale flux tube contrasts are confined to a few wavelengths and
  affected by scattered light and instrument defocus, even for space
  observations. <BR /> Methods: To test the contrast calculations,
  we compare rms contrasts from simulations with those obtained with
  the broad-band filter imager mounted on the Solar Optical Telescope
  (SOT) onboard the Hinode satellite and also analyse centre-to-limb
  variations (CLV). The 3-D MHD simulations include the interaction
  between convection and magnetic flux tubes. They are performed by
  assuming non-grey radiative transfer and using the MURaM code. The
  simulations have an average vertical magnetic field of 0 G, 50 G, and
  200 G. Emergent intensities are calculated with the spectral synthesis
  code ATLAS9 and are convolved with a theoretical point-spread function
  to account for the properties of the observations' optical system. <BR
  /> Results: We find reasonable agreement between simulated and observed
  intensity distributions in the visible continuum bands. Agreement is
  poorer for the CN and G-bands. The analysis of the simulations uncovers
  a potentially more realistic centre-to-limb behaviour than calculations
  based on 1-D model atmospheres. <BR /> Conclusions: We conclude that
  starting from 3-D MHD simulations represents a powerful approach
  to obtaining intensity contrasts for a wide wavelength coverage and
  different positions across on the solar disk. This also paves the way
  for future calculations of facular and network contrast as a function
  of magnetic fluxes.

Title: Towards a long-term record of solar total and spectral
    irradiance
Authors: Krivova, N. A.; Solanki, S. K.; Unruh, Y. C.
Bibcode: 2011JASTP..73..223K
Altcode: 2009arXiv0911.4002K
  The variation of total solar irradiance (TSI) has been measured since
  1978 and that of the spectral irradiance for an even shorter amount of
  time. Semi-empirical models are now available that reproduce over 80%
  of the measured irradiance variations. An extension of these models into
  the more distant past is needed in order to serve as input to climate
  simulations. Here we review our most recent efforts to model solar
  total and spectral irradiance on time scales from days to centuries and
  even longer. Solar spectral irradiance has been reconstructed since
  1947. Reconstruction of solar total irradiance goes back to 1610 and
  suggests a value of about 1-1.5W/m<SUP>2</SUP> for the increase in
  the cycle-averaged TSI since the end of the Maunder minimum, which
  is significantly lower than previously assumed but agrees with other
  modern models. First steps have also been made towards reconstructions
  of solar total and spectral irradiance on time scales of millennia.

Title: Magnetospheric accretion and spin-down of the prototypical
    classical T Tauri star AA Tau
Authors: Donati, J. -F.; Skelly, M. B.; Bouvier, J.; Gregory,
   S. G.; Grankin, K. N.; Jardine, M. M.; Hussain, G. A. J.; Ménard,
   F.; Dougados, C.; Unruh, Y.; Mohanty, S.; Aurière, M.; Morin, J.;
   Farès, R.; MAPP Collaboration
Bibcode: 2010MNRAS.409.1347D
Altcode: 2010arXiv1007.4407D; 2010MNRAS.tmp.1622D
  From observations collected with the ESPaDOnS spectropolarimeter
  at the Canada-France-Hawaii Telescope (CFHT) and with the NARVAL
  spectropolarimeter at the Télescope Bernard Lyot (TBL), we report the
  detection of Zeeman signatures on the prototypical classical T Tauri
  star AA Tau, both in photospheric lines and accretion-powered emission
  lines. Using time series of unpolarized and circularly polarized
  spectra, we reconstruct at two epochs maps of the magnetic field,
  surface brightness and accretion-powered emission of AA Tau. We find
  that AA Tau hosts a 2-3 kG magnetic dipole tilted at ≃20° to the
  rotation axis, and of presumably dynamo origin. We also show that the
  magnetic poles of AA Tau host large cool spots at photospheric level
  and accretion regions at chromospheric level. <P />The accretion rate
  at the surface of AA Tau at the time of our observations (estimated
  from the emission in the He I D<SUB>3</SUB> line mainly) is strongly
  variable, ranging from -9.6 to -8.5 and equal to -9.2 in average (in
  logarithmic scale and in M<SUB>⊙</SUB> yr<SUP>-1</SUP>); this is
  an order of magnitude smaller than the disc accretion rate at which
  the magnetic truncation radius (below which the disc is disrupted by
  the stellar magnetic field) matches the corotation radius (where the
  Keplerian period equals the stellar rotation period) - a necessary
  condition for accretion to occur. It suggests that AA Tau is largely
  in the propeller regime, with most of the accreting material in the
  inner disc regions being expelled outwards and only a small fraction
  accreted towards the surface of the star. The strong variability in
  the observed surface mass accretion rate and the systematic time-lag
  of optical occultations (by the warped accretion disc) with respect
  to magnetic and accretion-powered emission maxima also support this
  conclusion. <P />Our results imply that AA Tau is being actively
  spun-down by the star/disc magnetic coupling and appears as an ideal
  laboratory for studying angular momentum losses of forming suns in
  the propeller regime.

Title: IPHAS A-type Stars with Mid-IR Excesses in Spitzer Surveys
Authors: Hales, Antonio S.; Barlow, Michael J.; Drew, Janet E.; Unruh,
   Yvonne C.; Greimel, Robert; Irwin, Michael J.; González-Solares,
   Eduardo
Bibcode: 2010HiA....15..815H
Altcode:
  The Isaac Newton Photometric H-Alpha Survey (IPHAS) provides
  (r‧-Hα)-(r‧-i‧) colors, which can be used to select AV0-5 Main
  Sequence star candidates (age~20-200 Myr). By combining a sample of
  23050 IPHAS-selected A-type stars with 2MASS, GLIMPSE and MIPSGAL
  photometry we searched for mid-infrared excesses attributable to dusty
  circumstellar disks. Positional cross-correlation yielded a sample of
  2692 A-type stars, of which 0.6% were found to have 8-μm excesses above
  the expected photospheric values. The low fraction of main sequence
  stars with mid-IR excesses found in this work indicates that dust
  disks in the terrestrial planet zone of Main Sequence intermediate mass
  stars are rare. Dissipation mechanisms such as photo-evaporation, grain
  growth, collisional grinding or planet formation could possibly explain
  the depletion of dust detected in the inner regions of these disks.

Title: Quiet-sun Intensity Contrasts in the Near-ultraviolet as
    Measured from SUNRISE
Authors: Hirzberger, J.; Feller, A.; Riethmüller, T. L.; Schüssler,
   M.; Borrero, J. M.; Afram, N.; Unruh, Y. C.; Berdyugina, S. V.;
   Gandorfer, A.; Solanki, S. K.; Barthol, P.; Bonet, J. A.; Martínez
   Pillet, V.; Berkefeld, T.; Knölker, M.; Schmidt, W.; Title, A. M.
Bibcode: 2010ApJ...723L.154H
Altcode:
  We present high-resolution images of the Sun in the near-ultraviolet
  spectral range between 214 nm and 397 nm as obtained from the first
  science flight of the 1 m SUNRISE balloon-borne solar telescope. The
  quiet-Sun rms intensity contrasts found in this wavelength range are
  among the highest values ever obtained for quiet-Sun solar surface
  structures—up to 32.8% at a wavelength of 214 nm. We compare the
  rms contrasts obtained from the observational data with theoretical
  intensity contrasts obtained from numerical magnetohydrodynamic
  simulations. For 388 nm and 312 nm the observations agree well with
  the numerical simulations whereas at shorter wavelengths discrepancies
  between observed and simulated contrasts remain.

Title: Quiet-Sun intensity contrasts in the near ultraviolet
Authors: Hirzberger, Johann; Feller, Alex; Riethmüller, Tino L.;
   Schüssler, Manfred; Borrero, Juan M.; Afram, Nadine; Unruh, Yvonne C.;
   Berdyugina, Svetlana V.; Gandorfer, Achim; Solanki, Sami K.; Barthol,
   Peter; Bonet, Jose A.; Martínez Pillet, Valentin; Berkefeld, Thomas;
   Knölker, Michael; Schmidt, Wolfgang; Title, Alan M.
Bibcode: 2010arXiv1009.1050H
Altcode:
  We present high-resolution images of the Sun in the near ultraviolet
  spectral range between 214 nm and 397 nm as obtained from the first
  science flight of the 1-m Sunrise balloon-borne solar telescope. The
  quiet-Sun rms intensity contrasts found in this wavelength range
  are among the highest values ever obtained for quiet-Sun solar
  surface structures - up to 32.8% at a wavelength of 214 nm. We
  compare with theoretical intensity contrasts obtained from numerical
  magneto-hydrodynamic simulations. For 388 nm and 312 nm the observations
  agree well with the numerical simulations whereas at shorter wavelengths
  discrepancies between observed and simulated contrasts remain.

Title: Dynamo processes in the T Tauri star V410 Tau
Authors: Skelly, M. B.; Donati, J. -F.; Bouvier, J.; Grankin, K. N.;
   Unruh, Y. C.; Artemenko, S. A.; Petrov, P.
Bibcode: 2010MNRAS.403..159S
Altcode: 2009arXiv0911.5476S; 2010MNRAS.tmp..187S
  We present new brightness and magnetic images of the weak-line T Tauri
  star V410 Tau, made by using data from the Narval spectropolarimeter at
  Télescope Bernard Lyot (TBL). The brightness image shows a large polar
  spot and significant spot coverage at lower latitudes. The magnetic maps
  show a field that is predominantly dipolar and non-axisymmetric with a
  strong azimuthal component. The field is 50 per cent poloidal and 50
  per cent toroidal, and very little differential rotation is apparent
  from the magnetic images. <P />A photometric monitoring campaign on this
  star has previously revealed V-band variability of up to 0.6 mag, but in
  2009 the light curve is much flatter. The Doppler image presented here
  is consistent with this low variability. Calculating the flux predicted
  by the mapped spot distribution gives a peak-to-peak variability of
  0.04 mag. The reduction in the amplitude of the light curve, compared
  with previous observations, appears to be related to a change in the
  distribution of the spots rather than the number or area. <P />This
  paper is the first from a Zeeman-Doppler imaging campaign being carried
  out on V410 Tau between 2009 and 2012 at the TBL. During this time,
  it is expected that the light curve will return to a high-amplitude
  state, allowing us to ascertain whether the photometric changes are
  accompanied by a change in the magnetic field topology. <P />Based on
  observations obtained at the Télescope Bernard Lyot (TBL), operated
  by Centre national de la recherche scientifique/Institut national des
  sciences de l'Univers (CNRS/INSU) <P />E-mail: mskelly@ast.obs-mip.fr

Title: Complex magnetic topology and strong differential rotation
    on the low-mass T Tauri star V2247 Oph
Authors: Donati, J. -F.; Skelly, M. B.; Bouvier, J.; Jardine, M. M.;
   Gregory, S. G.; Morin, J.; Hussain, G. A. J.; Dougados, C.; Ménard,
   F.; Unruh, Y.
Bibcode: 2010MNRAS.402.1426D
Altcode: 2009arXiv0911.1080D; 2009MNRAS.tmp.1895D
  From observations collected with the ESPaDOnS spectropolarimeter
  at the Canada-France-Hawaii Telescope, we report the detection of
  Zeeman signatures on the low-mass classical T Tauri star (cTTS) V2247
  Oph. Profile distortions and circular polarization signatures detected
  in photospheric lines can be interpreted as caused by cool spots and
  magnetic regions at the surface of the star. The large-scale field
  is of moderate strength and highly complex; moreover, both the spot
  distribution and the magnetic field show significant variability on a
  time-scale of only 1 week, as a likely result of strong differential
  rotation. Both properties make V2247 Oph very different from the (more
  massive) prototypical cTTS BP Tau; we speculate that this difference
  reflects the lower mass of V2247 Oph. <P />During our observations,
  V2247 Oph was in a low-accretion state, with emission lines showing
  only weak levels of circular polarization; we nevertheless find that
  excess emission apparently concentrates in a mid-latitude region of a
  strong radial field, suggesting that it is the footpoint of an accretion
  funnel. <P />The weaker and more complex field that we report on V2247
  Oph may share similarities with those of very-low-mass late-M dwarfs
  and potentially explain why low-mass cTTSs rotate on average faster
  than intermediate-mass ones. These surprising results need confirmation
  from new independent data sets on V2247 Oph and other similar low-mass
  cTTSs. <P />Based on observations obtained at the Canada-France-Hawaii
  Telescope, operated by the National Research Council of Canada, the
  Institut National des Sciences de l'Univers of the Centre National de
  la Recherche Scientifique of France and the University of Hawaii. <P
  />E-mail: donati@ast.obs-mip.fr (J-FD); mskelly@ast.obs-mip.fr
  (MBS); jerome.bouvier@obs.ujf-grenoble.fr (JB); mmj@st-andrews.ac.uk
  (MMJ); sg64@st-andrews.ac.uk (SGG); jmorin@ast.obs-mip.fr (JM);
  ghussain@eso.org (GAJH); catherine.dougados@obs.ujf-grenoble.fr (CD);
  francois.menard@obs.ujf-grenoble.fr (FM); y.unruh@imperial.ac.uk (YU)

Title: VizieR Online Data Catalog: Simulated UVEX colors with
    reddening (Groot+, 2009)
Authors: Groot, P. J.; Verbeek, K.; Greimel, R.; Irwin, M.;
   Gonzalez-Solares, E.; Gansicke, B. T.; de Groot, E.; Drew, J.;
   Augusteijn, T.; Aungwerojwit, A.; Barlow, M.; Barros, S.; van den
   Besselaar, E. J. M.; Casares, J.; Corradi, R.; Corral-Santana, J. M.;
   Deacon, N.; van Ham, W.; Hu, H.; Heber, U.; Jonker, P. G.; King, R.;
   Knigge, C.; Mampaso, A.; Marsh, T. R.; Morales-Rueda, L.; Napiwotzki,
   R.; Naylor, T.; Nelemans, G.; Oosting, T.; Pyrzas, S.; Pretorius,
   M.; Rodriguez-Gil, P.; Roelofs, G. H. A.; Sale, S.; Schellart, P.;
   Steeghs, D.; Szyszka, C.; Unruh, Y.; Walton, N. A.; Weston, S.;
   Witham, A.; Woudt, P.; Zijlstra, A.
Bibcode: 2010yCat..73990323G
Altcode:
  To interpret the UVEX observations, simulations of the colours of stars
  and the effect of reddening are a very powerful and important tool. In
  obtaining the simulated colours, we follow the procedure as outlined
  in Drew et al. (2005MNRAS.362..753D) for the IPHAS. <P />(6 data files).

Title: A comparison of measured and simulated solar network contrast
Authors: Afram, N.; Unruh, Y. C.; Solanki, S. K.; Schüssler, M.;
   Mathew, S. K.
Bibcode: 2010IAUS..264...63A
Altcode: 2009arXiv0910.0976A
  Long-term trends in the solar spectral irradiance are important to
  determine the impact on Earth's climate. These long-term changes are
  thought to be caused mainly by changes in the surface area covered by
  small-scale magnetic elements. The direct measurement of the contrast
  to determine the impact of these small-scale magnetic elements
  is, however, limited to a few wavelengths, and is, even for space
  instruments, affected by scattered light and instrument defocus. In
  this work we calculate emergent intensities from 3-D simulations of
  solar magneto-convection and validate the outcome by comparing with
  observations from Hinode/SOT. In this manner we aim to construct the
  contrast at wavelengths ranging from the NUV to the FIR.

Title: The structure of the outer Galactic disc as revealed by IPHAS
    early A stars
Authors: Sale, S. E.; Drew, J. E.; Knigge, C.; Zijlstra, A. A.; Irwin,
   M. J.; Morris, R. A. H.; Phillipps, S.; Drake, J. J.; Greimel, R.;
   Unruh, Y. C.; Groot, P. J.; Mampaso, A.; Walton, N. A.
Bibcode: 2010MNRAS.402..713S
Altcode: 2009arXiv0909.3857S; 2009MNRAS.tmp.1816S
  This study is an investigation of the stellar density profile of the
  Galactic disc in the anticentre direction. We select over 40000 early
  A stars from INT/WFC Photometric Hα Survey of the Northern Galactic
  Plane (IPHAS) photometry in the Galactic longitude range 160° &lt;
  l &lt; 200° close to the equatorial plane (-1° &lt; b &lt; +1°). We
  then compare their observed reddening-corrected apparent magnitude
  distribution with simulated photometry obtained from parametrized
  models in order to set constraints on the anticentre stellar density
  profile. By selecting A stars, we are appraising the properties of a
  population only ~100 Myr old. We find that the stellar density profile
  of young stars is well fit to an exponential with length-scale of (3020
  +/- 120<SUB>statistical</SUB> +/- 180<SUB>systematic</SUB>) pc, which is
  comparable to that obtained in earlier studies, out to a Galactocentric
  radius of R<SUB>T</SUB> = (13.0 +/- 0.5<SUB>statistical</SUB> +/-
  0.6<SUB>systematic</SUB>) kpc. At larger radii, the rate of decline
  appears to increase with the scalelength dropping to (1200 +/-
  300<SUB>statistical</SUB> +/- 70<SUB>systematic</SUB>) pc. This result
  amounts to a refinement of the conclusions reached in previous studies
  that the stellar density profile is abruptly truncated. The IPHAS A
  star data are not compatible with models that propose a sudden change
  in metallicity at R<SUB>G</SUB> = 10 kpc.

Title: IPHAS and the symbiotic stars . II. New discoveries and a
    sample of the most common mimics
Authors: Corradi, R. L. M.; Valentini, M.; Munari, U.; Drew, J. E.;
   Rodríguez-Flores, E. R.; Viironen, K.; Greimel, R.; Santander-García,
   M.; Sabin, L.; Mampaso, A.; Parker, Q.; DePew, K.; Sale, S. E.; Unruh,
   Y. C.; Vink, J. S.; Rodríguez-Gil, P.; Barlow, M. J.; Lennon, D. J.;
   Groot, P. J.; Giammanco, C.; Zijlstra, A. A.; Walton, N. A.
Bibcode: 2010A&A...509A..41C
Altcode: 2009arXiv0910.5930C
  Context. Knowledge of the total population of symbiotic stars in
  the Galaxy is important for understanding basic aspects of stellar
  evolution in interacting binaries and the relevance of this class
  of objects in the formation of supernovae of type Ia. <BR /> Aims:
  In a previous paper, we presented the selection criteria needed to
  search for symbiotic stars in IPHAS, the INT Hα survey of the Northern
  Galactic plane. IPHAS gives us the opportunity to make a systematic,
  complete search for symbiotic stars in a magnitude-limited volume. <BR
  /> Methods: Follow-up spectroscopy at different telescopes worldwide
  of a sample of sixty two symbiotic star candidates is presented. <BR
  /> Results: Seven out of nineteen S-type candidates observed
  spectroscopically are confirmed to be genuine symbiotic stars. The
  spectral type of their red giant components, as well as reddening
  and distance, were computed by modelling the spectra. Only one new
  D-type symbiotic system, out of forty-three candidates observed,
  was found. This was as expected (see discussion in our paper on the
  selection criteria). The object shows evidence for a high density
  outflow expanding at a speed ≥65 km s<SUP>-1</SUP>. Most of the
  other candidates are lightly reddened classical T Tauri stars and
  more highly reddened young stellar objects that may be either more
  massive young stars of HAeBe type or classical Be stars. In addition,
  a few notable objects have been found, such as three new Wolf-Rayet
  stars and two relatively high-luminosity evolved massive stars. We also
  found a helium-rich source, possibly a dense ejecta hiding a WR star,
  which is surrounded by a large ionized nebula. <BR /> Conclusions:
  These spectroscopic data allow us to refine the selection criteria for
  symbiotic stars in the IPHAS survey and, more generally, to better
  understand the behaviour of different Hα emitters in the IPHAS and
  2MASS colour-colour diagrams. <P />Based on observations obtained at;
  the 2.6 m Nordic Optical Telescope operated by NOTSA; the 2.5 m INT
  and 4.2 m WHT telescopes of the Isaac Newton Group of Telescopes in
  the Spanish Observatorio del Roque de Los Muchachos of the Instituto
  de Astrofísica de Canarias; the 2.3 m ANU telescope at Siding Spring
  Observatory, Australia; the Asiago 1.82 m telescope of the INAF
  Astronomical Observatory of Padova, Italy; and the 2.1 m telescope
  at San Pedro Martir, Mexico. Some of the INT spectra incorporated
  into this paper were obtained as part of a CCI International Time
  Programme awarded to the IPHAS collaboration. This publication makes
  use of data products from the Two Micron All Sky Survey, which is
  a joint project of the University of Massachusetts and the Infrared
  Processing and Analysis Center/California Institute of Technology,
  funded by the National Aeronautics and Space Administration and the
  National Science Foundation. This research has also made use of the
  SIMBAD database, operated at CDS, Strasbourg, France.

Title: Modelling rotational and cyclical spectral solar irradiance
    variations
Authors: Unruh, Yvonne
Bibcode: 2010cosp...38...18U
Altcode: 2010cosp.meet...18U
  Solar irradiance changes are highly wavelength dependent: solar-cycle
  variations in the UV can be on the order of tens of percent, while
  changes in the visible are typically only of the order of one or two
  permille. With the launch of a number of instruments to measure spectral
  solar irradiance, we are now for a first time in a good position to
  explore the changing solar irradiance over a large range of wavelengths
  and to test our irradiance models as well as some of their underlying
  assumptions. I will introduce some of the current modelling approaches
  and present model-data comparisons, using the SATIRE irradiance
  model and SORCE/SIM measurements as an example. I will conclude by
  highlighting a number of outstanding questions regarding the modelling
  of spectral irradiance and current approaches to address these.

Title: Total and spectral irradiance comparisons between SIM and
    the SATIRE model in the declining phase of cycle 23
Authors: Ball, Will; Unruh, Yvonne; Krivova, Natalie; Solanki, Sami
   K.; Harder, Jerald
Bibcode: 2010cosp...38..136B
Altcode: 2010cosp.meet..136B
  Climate models rely on accurate total and spectral solar irradiance
  inputs, but until 2003 con-tinuous spectral irradiance information
  across a large portion of the solar spectrum was lacking. Since the
  launch of the Solar Radiation and Climate Experiment (SORCE), with the
  Spectral Irradiance Monitor (SIM) observing the UV, visible and IR,
  data have been accumulating and now cover a significant portion of
  a cycle. For the first time this allows spectral models to be tested
  over periods greater than a solar rotation. We present six years of
  total and spectral irradiance reconstructions using the SATIRE model
  that incorporates SOHO/MDI continuum and magnetogram images for the
  period April 2004 to November 2009 in the declining phase of cycle 23
  and through the recent unusual minimum. We compare these results with
  the SIM instrument and so cover the spectral region 200 -1600 nm. While
  detrended, short-term, variation is recreated well by the model, there
  are discrepancies in longer-term trends between observations and the
  model. This may become important when considering the radiative forcing
  from the Sun used in climate research and so understanding why there is
  such a significant disagreement is an important area of investigation.

Title: Near-IR spectra of IPHAS extremely red Galactic AGB stars
Authors: Wright, N. J.; Barlow, M. J.; Greimel, R.; Drew, J. E.;
   Matsuura, M.; Unruh, Y. C.; Zijlstra, A. A.
Bibcode: 2009MNRAS.400.1413W
Altcode: 2009arXiv0909.2642W; 2009MNRAS.tmp.1324W
  We present a library of 139 near-IR spectra of cool asymptotic giant
  branch stars that will be useful for comparison with theoretical
  model atmosphere calculations and for modelling the integrated
  emission from intermediate-age stellar populations. The source list
  was selected from the `extremely red' region of the Isaac Newton
  Telescope (INT) Photometric Hα Survey (IPHAS) colour-colour plane
  that is overwhelmingly dominated by very late-type stars. The spectral
  library also includes a large fraction of S-type and carbon stars. We
  present a number of spectral classification sequences highlighting
  the various molecular features identified and discuss a number of
  rare features with uncertain identifications in the literature. With
  its focus on particularly cool photospheres, this catalogue serves
  as a companion to recent spectroscopic atlases of MK standards in the
  near-IR. Finally, the relationship between IPHAS (r' - i') and (r' -
  Hα) colours and spectroscopically determined properties is discussed
  and a strong correlation between the (r' - Hα) colour and the C/O
  abundance index for S-type and carbon stars is noted. This relation
  has the potential to separate O-rich, S-type and carbon stars in the
  Galaxy based on their photometry alone.

Title: Doppler images and chromospheric variability of TWA 17
Authors: Skelly, M. B.; Unruh, Y. C.; Barnes, J. R.; Lawson, W. A.;
   Donati, J. -F.; Collier Cameron, A.
Bibcode: 2009MNRAS.399.1829S
Altcode: 2009arXiv0907.2777S
  We present Doppler imaging and a Balmer line analysis of the
  weak-line T Tauri star TWA 17. Spectra were taken in 2006 with the
  University College London Echelle Spectrograph on the Anglo-Australian
  Telescope. Using least-squares deconvolution to improve the effective
  signal-to-noise ratio, we produced a Doppler map of the surface spot
  distribution. This shows similar features to maps of other rapidly
  rotating T Tauri stars, i.e. a polar spot with more spots extending
  out of it down to the equator. <P />In addition to the photospheric
  variability, the chromospheric variability was studied using the Balmer
  emission. The mean Hα profile has a narrow component consistent with
  rotational broadening and a broad component extending out to 220 km
  s<SUP>-1</SUP>. The variability in Hα suggests that the chromosphere
  has at least one slingshot prominence 3R<SUB>*</SUB> above the surface.

Title: VizieR Online Data Catalog: Near-IR spectra of extremely red
    AGB stars (Wright+, 2009)
Authors: Wright, N. J.; Barlow, M. J.; Greimel, R.; Drew, J. E.;
   Matsuura, M.; Unruh, Y. C.; Zijlstra, A. A.
Bibcode: 2009yCat..74001413W
Altcode:
  No abstract at ADS

Title: The UV-Excess survey of the northern Galactic plane
Authors: Groot, Paul J.; Verbeek, Kars; Greimel, Robert; Irwin, Mike;
   González-Solares, Eduardo; Gänsicke, Boris T.; de Groot, Eelco;
   Drew, Janet; Augusteijn, Thomas; Aungwerojwit, Amornrat; Barlow,
   Mike; Barros, Susana; van den Besselaar, Else J. M.; Casares, Jorge;
   Corradi, Romano; Corral-Santana, Jesús M.; Deacon, Niall; van Ham,
   Wilbert; Hu, Haili; Heber, Uli; Jonker, Peter G.; King, Rob; Knigge,
   Christian; Mampaso, Antonio; Marsh, Tom R.; Morales-Rueda, Luisa;
   Napiwotzki, Ralf; Naylor, Tim; Nelemans, Gijs; Oosting, Tim; Pyrzas,
   Stylianos; Pretorius, Magaretha; Rodríguez-Gil, Pablo; Roelofs,
   Gijs H. A.; Sale, Stuart; Schellart, Pim; Steeghs, Danny; Szyszka,
   Cezary; Unruh, Yvonne; Walton, Nicholas A.; Weston, Simon; Witham,
   Andrew; Woudt, Patrick; Zijlstra, Albert
Bibcode: 2009MNRAS.399..323G
Altcode: 2009arXiv0906.3498G; 2009MNRAS.tmp.1184G
  The UV-Excess survey of the northern Galactic plane images a
  10° × 185° wide band, centred on the Galactic equator using
  the 2.5-m Isaac Newton Telescope in four bands (I5875) down to
  ~21-22 mag ( in I5875). The setup and data reduction procedures are
  described. Simulations of the colours of main-sequence stars, giant,
  supergiants, DA and DB white dwarfs and AM Canum Venaticorum stars are
  made, including the effects of reddening. A first look at the data of
  the survey (currently 30 per cent complete) is given.

Title: Solar Surface Magnetism and Irradiance on Time Scales from
    Days to the 11-Year Cycle
Authors: Domingo, V.; Ermolli, I.; Fox, P.; Fröhlich, C.; Haberreiter,
   M.; Krivova, N.; Kopp, G.; Schmutz, W.; Solanki, S. K.; Spruit, H. C.;
   Unruh, Y.; Vögler, A.
Bibcode: 2009SSRv..145..337D
Altcode:
  The uninterrupted measurement of the total solar irradiance during the
  last three solar cycles and an increasing amount of solar spectral
  irradiance measurements as well as solar imaging observations
  (magnetograms and photometric data) have stimulated the development
  of models attributing irradiance variations to solar surface
  magnetism. Here we review the current status of solar irradiance
  measurements and modelling efforts based on solar photospheric
  magnetic fields. Thereby we restrict ourselves to the study of solar
  variations from days to the solar cycle. Phenomenological models
  of the solar atmosphere in combination with imaging observations of
  solar electromagnetic radiation and measurements of the photospheric
  magnetic field have reached high enough quality to show that a large
  fraction (at least, about 80%) of the solar irradiance variability
  can be explained by the radiative effects of the magnetic activity
  present in the photosphere. Also, significant progress has been made
  with magnetohydrodynamic simulations of convection that allow us to
  relate the radiance of the photospheric magnetic structures to the
  observations.

Title: An IPHAS-based search for accreting very low-mass objects
    using VO tools
Authors: Valdivielso, L.; Martín, E. L.; Bouy, H.; Solano, E.; Drew,
   J. E.; Greimel, R.; Gutiérrez, R.; Unruh, Y. C.; Vink, J. S.
Bibcode: 2009mavo.proc..175V
Altcode:
  We prove that accreting very low-mass (VLM) stars and brown dwarfs (BDs)
  can be identified in IPHAS, an Hα emission survey of the northern Milky
  Way. Full exploitation of the IPHAS database and a future extension
  of it in the southern hemisphere will be useful in identifying
  VLM accreting objects near to and far from well-known star-forming
  regions. We have used Virtual Observatory (VO) tools to cross-match
  the IPHAS catalogue with the 2MASS catalogue. We defined photometric
  criteria to identify Hα emission sources with near-infrared colours
  similar to those of known young VLM stars and BDs. 4000 candidates were
  identified that met our criteria over an area of 1600 square degrees.

Title: New young planetary nebulae in IPHAS
Authors: Viironen, K.; Mampaso, A.; Corradi, R. L. M.; Rodríguez,
   M.; Greimel, R.; Sabin, L.; Sale, S. E.; Unruh, Y.; Delgado-Inglada,
   G.; Drew, J. E.; Giammanco, C.; Groot, P.; Parker, Q. A.; Sokoloski,
   J.; Zijlstra, A.
Bibcode: 2009A&A...502..113V
Altcode: 2009arXiv0904.1937V
  Aims: We search for very small-diameter galactic planetary nebulae
  (PNe) representing the earliest phases of PN evolution. The IPHAS
  catalogue of Hα-emitting stars provides a useful basis for this study
  since all sources present in this catalogue must be of small angular
  diameter. <BR />Methods: The PN candidates are selected based on their
  location in two colour-colour diagrams: IPHAS (r' - Hα) vs. (r' - i'),
  and 2MASS (J - H) vs. (H - K_s). Spectroscopic follow-up was carried
  out on a sample of candidates to confirm their nature. <BR />Results:
  We present a total of 83 PN candidates. We were able to obtain spectra
  or find the classification from the literature for 35 candidates. Five
  of these objects are likely to be new PNe, including one large bipolar
  PN discovered serendipitously close to an emission-line star. PN
  distances deduced from extinction-distance relations based on IPHAS
  field-star photometry are presented for the first time. These yield
  distance estimates for our objects in the range 2 kpc and 6 kpc. From
  the data in hand, we conclude that four of the discovered objects are
  probably young PNe.

Title: An IPHAS-based search for accreting very low-mass objects
    using VO tools
Authors: Valdivielso, L.; Martín, E. L.; Bouy, H.; Solano, E.; Drew,
   J. E.; Greimel, R.; Gutiérrez, R.; Unruh, Y. C.; Vink, J. S.
Bibcode: 2009A&A...497..973V
Altcode: 2008arXiv0810.4042V
  Context: The main goal of this paper is to prove that accreting very
  low-mass stars and brown dwarfs can be identified in IPHAS, an Hα
  emission survey of the northern Milky Way. Full exploitation of the
  IPHAS database and a future extension of it in the southern hemisphere
  will be useful in identifying very low-mass accreting objects near
  to and far from well-known star-forming regions. <BR />Aims: We have
  used Virtual Observatory tools to cross-match the IPHAS catalogue
  with the 2MASS catalogue. We defined photometric criteria to identify
  Hα emission sources with near-infrared colours similar to those of
  known young very low-mass stars and brown dwarfs. 4000 candidates were
  identified that met our criteria over an area of 1600 square degrees. We
  present low-resolution optical spectra of 113 candidates. Spectral types
  have been derived for the 33 candidates that have spectroscopically
  confirmed Hα emission, negligible reddening and spectral class M. We
  have also measured Hα emission and investigated the NaI doublet (818.3
  nm, 819.5 nm) in these 33 objects. <BR />Methods: We confirm that 33
  IPHAS candidates have strong Hα emission indicative of disc accretion
  for their spectral type. Twenty-three of them have spectral class M4 or
  later, of which ten have classes in the range M5.5-M7.0 and could thus
  be very young brown dwarfs. Many objects also have a weak NaI doublet,
  an indication of low surface gravity. <BR />Results: IPHAS provides a
  very valuable database for identifying accreting very low-mass stars
  and brown dwarfs. Virtual Observatory tools provide an efficient method
  for identifying these objects over large areas of the sky. Based on our
  success rate of 23 Hα emission objects with spectral type in the range
  M4-M7 out of 113 candidates with spectroscopic follow-up, we estimate
  that there could be hundreds of such objects in the full IPHAS survey.

Title: Iphas A-Type Stars with Mid-Infrared Excesses in Spitzer
    Surveys
Authors: Hales, Antonio S.; Barlow, Michael J.; Drew, Janet E.; Unruh,
   Yvonne C.; Greimel, Robert; Irwin, Michael J.; González-Solares,
   Eduardo
Bibcode: 2009ApJ...695...75H
Altcode: 2009arXiv0901.0909H
  We have identified 17 A-type stars in the Galactic Plane that have
  mid-infrared (mid-IR) excesses at 8 μm. From observed colors in the
  (r' - Hα) - (r' - i') plane, we first identified 23,050 early A-type
  main-sequence (MS) star candidates in the Isaac Newton Photometric
  H-Alpha Survey (IPHAS) point source database that are located in
  Spitzer Galactic Legacy Mid-Plane Survey Extraordinaire Galactic plane
  fields. Imposing the requirement that they be detected in all seven
  Two Micron All Sky Survey and Infrared Astronomical Satellite bands
  led to a sample of 2692 candidate A-type stars with fully sampled 0.6
  to 8 μm spectral energy distributions (SEDs). Optical classification
  spectra of 18 of the IPHAS candidate A-type MS stars showed that all
  but one could be well fitted using MS A-type templates, with the other
  being an A-type supergiant. Out of the 2692 A-type candidates 17 (0.6%)
  were found to have 8 μm excesses above the expected photospheric
  values. Taking into account non-A-Type contamination estimates, the 8
  μm excess fraction is adjusted to ~0.7%. The distances to these sources
  range from 0.7 to 2.5 kpc. Only 10 out of the 17 excess stars had been
  covered by Spitzer MIPSGAL survey fields, of which five had detectable
  excesses at 24 μm. For sources with excesses detected in at least two
  mid-IR wavelength bands, blackbody fits to the excess SEDs yielded
  temperatures ranging from 270 to 650 K, and bolometric luminosity
  ratios L <SUB>IR</SUB>/L <SUB>sstarf</SUB> from 2.2 × 10<SUP>-3</SUP>
  - 1.9 × 10<SUP>-2</SUP>, with a mean value of 7.9 × 10<SUP>-3</SUP>
  (these bolometric luminosities are lower limits as cold dust is not
  detectable by this survey). Both the presence of mid-IR excesses and
  the derived bolometric luminosity ratios are consistent with many of
  these systems being in the planet-building transition phase between
  the early protoplanetary disk phase and the later debris disk phase.

Title: High spatial resolution empirical 3D extinction mapping
    with IPHAS
Authors: Sale, S. E.; Drew, J. E.; Greimel, R.; Unruh, Y. C.; IPHAS
   Consortium
Bibcode: 2009IAUS..254P..67S
Altcode:
  No abstract at ADS

Title: Towards Long-Term Solar Irradiance Modelling: Network Contrasts
    from Magneto-Convection Simulations
Authors: Unruh, Y. C.; Solanki, S. K.; Schüssler, M.; Vögler, A.;
   Garcia-Alvarez, D.
Bibcode: 2009AIPC.1094..768U
Altcode: 2009csss...15..768U
  Solar irradiance changes on a wide range of time scales and is a key
  driver of the Earth's climate where secular variability in particular is
  relevant. This is, however, not well understood and our knowledge relies
  on reconstructions based on sunspot numbers and similar proxies. <P
  />The prime candidate to produce secular variability is a change
  in the surface coverage of small-scale magnetic elements. Direct
  observational determination of the flux emitted by these magnetic
  elements is difficult, especially as information covering a large
  spectral range is needed. Here we present a theoretical approach
  to this problem using intensity calculations from 3-D simulations
  of solar magneto-convection and compare these with the intensity
  calculations used in the successful semi-empirical S ATIRE models at
  disk centre. Eventually, such a comparison should lead to the removal
  of the last free parameter from S ATIRE-based irradiance reconstruction.

Title: High spatial resolution Galactic 3D extinction mapping
    with IPHAS
Authors: Sale, Stuart E.; Drew, J. E.; Unruh, Y. C.; Irwin, M. J.;
   Knigge, C.; Phillipps, S.; Zijlstra, A. A.; Gänsicke, B. T.; Greimel,
   R.; Groot, P. J.; Mampaso, A.; Morris, R. A. H.; Napiwotzki, R.;
   Steeghs, D.; Walton, N. A.
Bibcode: 2009MNRAS.392..497S
Altcode: 2008arXiv0810.2547S
  We present an algorithm (MEAD, for `Mapping Extinction Against
  Distance') which will determine intrinsic (r' - i') colour, extinction,
  and distance for early-A to K4 stars extracted from the IPHAS r'/i'/Hα
  photometric data base. These data can be binned up to map extinction in
  three dimensions across the northern Galactic plane. The large size of
  the IPHAS data base (~200 million unique objects), the accuracy of the
  digital photometry it contains and its faint limiting magnitude (r'
  ~ 20) allow extinction to be mapped with fine angular (~10 arcmin)
  and distance (~ 0.1 kpc) resolution to distances of up to 10 kpc,
  outside the solar circle. High reddening within the solar circle on
  occasion brings this range down to ~2 kpc. The resolution achieved,
  both in angle and depth, greatly exceeds that of previous empirical
  3D extinction maps, enabling the structure of the Galactic Plane to be
  studied in increased detail. MEAD accounts for the effect of the survey
  magnitude limits, photometric errors, unresolved interstellar medium
  (ISM) substructure and binarity. The impact of metallicity variations,
  within the range typical of the Galactic disc is small. The accuracy and
  reliability of MEAD are tested through the use of simulated photometry
  created with Monte Carlo sampling techniques. The success of this
  algorithm is demonstrated on a selection of fields and the results
  are compared to the literature.

Title: Extremely red stellar objects revealed by IPHAS
Authors: Wright, N. J.; Greimel, R.; Barlow, M. J.; Drew, J. E.; Cioni,
   M. -R. L.; Zijlstra, A. A.; Corradi, R. L. M.; González-Solares,
   E. A.; Groot, P.; Irwin, J.; Irwin, M. J.; Mampaso, A.; Morris,
   R. A. H.; Steeghs, D.; Unruh, Y. C.; Walton, N.
Bibcode: 2008MNRAS.390..929W
Altcode: 2008MNRAS.tmp.1113W; 2008arXiv0808.2441W
  We present photometric analysis and follow-up spectroscopy for
  a population of extremely red stellar objects extracted from the
  point-source catalogue of the Isaac Newton Telescope (INT) Photometric
  Hα Survey (IPHAS) of the northern Galactic plane. The vast majority
  of these objects have no previous identification. Analysis of optical,
  near- and mid-infrared photometry reveals that they are mostly highly
  reddened asymptotic giant branch stars, with significant levels of
  circumstellar material. We show that the distribution of these objects
  traces galactic extinction, their highly reddened colours being a
  product of both interstellar and circumstellar reddening. This is
  the first time that such a large sample of evolved low-mass stars
  has been detected in the visual and allows optical counterparts to be
  associated with sources from recent infrared surveys. <P />Follow-up
  spectroscopy on some of the most interesting objects in the sample has
  found significant numbers of S-type stars which can be clearly separated
  from oxygen-rich objects in the IPHAS colour-colour diagram. We show
  that this is due to the positions of different molecular bands relative
  to the narrow-band Hα filter used for IPHAS observations. The IPHAS
  (r' - Hα) colour offers a valuable diagnostic for identifying S-type
  stars. A selection method for identifying S-type stars in the Galactic
  plane is briefly discussed and we estimate that over a thousand new
  objects of this type may be discovered, potentially doubling the number
  of known objects in this short but important evolutionary phase.

Title: IPHAS identification of IGR J19267+1325 as a Cataclysmic
    Variable
Authors: Steeghs, D.; Knigge, C.; Drew, J.; Unruh, Y.; Greimel, R.
Bibcode: 2008ATel.1653....1S
Altcode:
  We report on optical observations of the galactic plane containing
  the X-ray source IGR J19267+1325=1RXS J192626.8+132153 (ATEL
  #1649,#1323) using data from the INT Photometric H-Alpha Survey (IPHAS;
  http://www.iphas.org ). The field containing the X-ray source was
  observed in good observing conditions on August 22 2004 using the Isaac
  Newton Telescope at La Palma Observatory and its Wide Field Camera.

Title: Initial data release from the INT Photometric Hα Survey of
    the Northern Galactic Plane (IPHAS)
Authors: González-Solares, E. A.; Walton, N. A.; Greimel, R.; Drew,
   J. E.; Irwin, M. J.; Sale, S. E.; Andrews, K.; Aungwerojwit, A.;
   Barlow, M. J.; van den Besselaar, E.; Corradi, R. L. M.; Gänsicke,
   B. T.; Groot, P. J.; Hales, A. S.; Hopewell, E. C.; Hu, Haili; Irwin,
   J.; Knigge, C.; Lagadec, E.; Leisy, P.; Lewis, J. R.; Mampaso, A.;
   Matsuura, M.; Moont, B.; Morales-Rueda, L.; Morris, R. A. H.; Naylor,
   T.; Parker, Q. A.; Prema, P.; Pyrzas, S.; Rixon, G. T.; Rodríguez-Gil,
   P.; Roelofs, G.; Sabin, L.; Skillen, I.; Suso, J.; Tata, R.; Viironen,
   K.; Vink, J. S.; Witham, A.; Wright, N. J.; Zijlstra, A. A.; Zurita,
   A.; Drake, J.; Fabregat, J.; Lennon, D. J.; Lucas, P. W.; Martín,
   E. L.; Phillipps, S.; Steeghs, D.; Unruh, Y. C.
Bibcode: 2008MNRAS.388...89G
Altcode: 2008MNRAS.tmp..707G; 2007arXiv0712.0384G
  The INT/WFC Photometric Hα Survey of the Northern Galactic Plane
  (IPHAS) is an imaging survey being carried out in Hα, r' and i'
  filters, with the Wide Field Camera (WFC) on the 2.5-m Isaac Newton
  Telescope (INT) to a depth of r' = 20 (10σ). The survey is aimed
  at revealing the large scale organization of the Milky Way and
  can be applied to identifying a range of stellar populations within
  it. Mapping emission line objects enables a particular focus on objects
  in the young and old stages of stellar evolution ranging from early
  T-Tauri stars to late planetary nebulae. In this paper we present
  the IPHAS Initial Data Release, primarily a photometric catalogue
  of about 200 million unique objects, coupled with associated image
  data covering about 1600 deg<SUP>2</SUP> in three passbands. We note
  how access to the primary data products has been implemented through
  use of standard virtual observatory publishing interfaces. Simple
  traditional web access is provided to the main IPHAS photometric
  catalogue, in addition to a number of common catalogues (such as
  2MASS) which are of immediate relevance. Access through the AstroGrid
  VO Desktop opens up the full range of analysis options, and allows
  full integration with the wider range of data and services available
  through the Virtual Observatory. The IDR represents the largest data
  set published primarily through VO interfaces to date, and so stands
  as an exemplar of the future of survey data mining. Examples of data
  access are given, including a cross-matching of IPHAS photometry with
  sources in the UKIDSS Galactic Plane Survey that validates the existing
  calibration of the best data.

Title: Spectral irradiance variations: comparison between observations
    and the SATIRE model on solar rotation time scales
Authors: Unruh, Y. C.; Krivova, N. A.; Solanki, S. K.; Harder, J. W.;
   Kopp, G.
Bibcode: 2008A&A...486..311U
Altcode: 2008arXiv0802.4178U
  Aims: We test the reliability of the observed and calculated spectral
  irradiance variations between 200 and 1600 nm over a time span of
  three solar rotations in 2004. <BR />Methods: We compare our model
  calculations to spectral irradiance observations taken with SORCE/SIM,
  SoHO/VIRGO, and UARS/SUSIM. The calculations assume LTE and are based
  on the SATIRE (Spectral And Total Irradiance REconstruction) model. We
  analyse the variability as a function of wavelength and present time
  series in a number of selected wavelength regions covering the UV to
  the NIR. We also show the facular and spot contributions to the total
  calculated variability. <BR />Results: In most wavelength regions,
  the variability agrees well between all sets of observations and the
  model calculations. The model does particularly well between 400 and
  1300 nm, but fails below 220 nm, as well as for some of the strong NUV
  lines. Our calculations clearly show the shift from faculae-dominated
  variability in the NUV to spot-dominated variability above approximately
  400 nm. We also discuss some of the remaining problems, such as the low
  sensitivity of SUSIM and SORCE for wavelengths between approximately
  310 and 350 nm, where currently the model calculations still provide
  the best estimates of solar variability.

Title: Magnetospheric accretion on the T Tauri star BP Tauri
Authors: Donati, J. -F.; Jardine, M. M.; Gregory, S. G.; Petit, P.;
   Paletou, F.; Bouvier, J.; Dougados, C.; Ménard, F.; Collier Cameron,
   A.; Harries, T. J.; Hussain, G. A. J.; Unruh, Y.; Morin, J.; Marsden,
   S. C.; Manset, N.; Aurière, M.; Catala, C.; Alecian, E.
Bibcode: 2008MNRAS.386.1234D
Altcode: 2008MNRAS.tmp..461D; 2008arXiv0802.2052D
  From observations collected with the ESPaDOnS and NARVAL
  spectropolarimeters, we report the detection of Zeeman signatures
  on the classical T Tauri star (cTTS) BP Tau. Circular polarization
  signatures in photospheric lines and in narrow emission lines
  tracing magnetospheric accretion are monitored throughout most of
  the rotation cycle of BP Tau at two different epochs in 2006. We
  observe that rotational modulation dominates the temporal variations
  of both unpolarized and circularly polarized spectral proxies tracing
  the photosphere and the footpoints of accretion funnels. <P />From
  the complete data sets at each epoch, we reconstruct the large-scale
  magnetic topology and the location of accretion spots at the surface
  of BP Tau using tomographic imaging. We find that the field of BP Tau
  involves a 1.2 kG dipole and 1.6 kG octupole, both slightly tilted with
  respect to the rotation axis. Accretion spots coincide with the two main
  magnetic poles at high latitudes and overlap with dark photospheric
  spots; they cover about 2 per cent of the stellar surface. The strong
  mainly axisymmetric poloidal field of BP Tau is very reminiscent
  of magnetic topologies of fully convective dwarfs. It suggests that
  magnetic fields of fully convective cTTSs such as BP Tau are likely not
  fossil remants, but rather result from vigorous dynamo action operating
  within the bulk of their convective zones. <P />Preliminary modelling
  suggests that the magnetosphere of BP Tau extends to distances of at
  least 4R<SUB>*</SUB> to ensure that accretion spots are located at high
  latitudes, and is not blown open close to the surface by a putative
  stellar wind. It apparently succeeds in coupling to the accretion
  disc as far out as the corotation radius, and could possibly explain
  the slow rotation of BP Tau. <P />Based on observations obtained
  at the Canada-France-Hawaii Telescope (CFHT) and at the Télescope
  Bernard Lyot (TBL). CFHT is operated by the National Research Council
  of Canada, the Institut National des Sciences de l'Univers of the
  Centre National de la Recherche Scientifique of France (INSU/CNRS)
  and the University of Hawaii, while TBL is operated by CNRS/INSU. <P
  />E-mail: donati@ast.obs-mip.fr (J-FD); mmj@st-andrews.ac.uk
  (MMJ); sg64@st-andrews.ac.uk (SGG); petit@ast.obs-mip.fr (PP);
  fpaletou@ast.obs-mip.fr (FP); jerome.bouvier@obs.ujf-grenoble.fr
  (JB); catherine.dougados@obs.ujf-grenoble.fr (CD);
  francois.menard@obs.ujf-grenoble.fr (FM); acc4@st-andrews.ac.uk
  (ACC); th@astro.ex.ac.uk (TJH); ghussain@eso.org (GAJH);
  y.unruh@imperial.ac.uk (YU); jmorin@ast.obs-mip.fr (JM); scm@aao.gov.au
  (SCM); manset@cfht.hawaii.edu (NM); auriere@ast.obs-mip.fr (MA);
  claude.catala@obspm.fr (CC); evelyne.alecian@obspm.fr (EA)

Title: Doppler images and chromospheric variability of TWA 6
Authors: Skelly, M. B.; Unruh, Y. C.; Collier Cameron, A.; Barnes,
   J. R.; Donati, J. -F.; Lawson, W. A.; Carter, B. D.
Bibcode: 2008MNRAS.385..708S
Altcode: 2008MNRAS.tmp..221S; 2008arXiv0801.0541S
  We present Doppler imaging and Balmer line analysis of the weak-line
  T Tauri star TWA 6. Using these data we have made one of the first
  attempts to measure differential rotation in a T Tauri star, and the
  first detection of a slingshot prominence in such a star. We also
  show the most direct evidence to date of the existence of solar-type
  plages in a star other than the Sun. <P />Observations were made
  over six nights: 2006 February 11-13 and 2006 February 18-20, when
  spectra were taken with the UCL Echelle Spectrograph on the 3.9-m
  Anglo-Australian Telescope. Using least-squares deconvolution to
  improve the effective signal-to-noise ratio we produced two Doppler
  maps. These show similar features to maps of other rapidly rotating T
  Tauri stars, i.e. a polar spot with more spots extending out of it down
  to equator. Comparison of the two maps was carried out to measure the
  differential rotation. Cross-correlation and parameter fitting indicates
  that TWA 6 does not have detectable differential rotation. <P />The
  Balmer emission of the star was studied. The mean Hα profile has a
  narrow component consistent with rotational broadening and a broad
  component extending out to +/-250kms<SUP>-1</SUP>. The variability
  in Hα suggests that the chromosphere has active regions that are
  cospatial with the spots in the photosphere, similar to the `plages'
  observed on the Sun. In addition the star has at least one slingshot
  prominence 3R<SUB>*</SUB> above the surface - the first such detection
  in a T Tauri star.

Title: Five WC9 stars discovered in the AAO/UKST Hα survey
Authors: Hopewell, E. C.; Barlow, M. J.; Drew, J. E.; Unruh, Y. C.;
   Parker, Q. A.; Pierce, M. J.; Crowther, P. A.; Knigge, C.; Phillipps,
   S.; Zijlstra, A. A.
Bibcode: 2005MNRAS.363..857H
Altcode: 2005MNRAS.tmp..842H; 2005astro.ph..8187H
  We report the discovery of five massive Wolf-Rayet (WR) stars resulting
  from a programme of follow-up spectroscopy of candidate emission-line
  stars in the Anglo-Australian Observatory United Kingdom Schmidt
  Telescope (AAO/UKST) Southern Galactic Plane Hα survey. The 6195-6775
  Åspectra of the stars are presented and discussed. A WC9 class is
  assigned to all five stars through comparison of their spectra with
  those of known late-type WC stars, bringing the known total number of
  Galactic WC9 stars to 44. Whilst three of the five WC9 stars exhibit
  near-infrared (NIR) excesses characteristic of hot dust emission (as
  seen in the great majority of known WC9 stars), we find that two of
  the stars show no discernible evidence of such excesses. This increases
  the number of known WC9 stars without NIR excesses to seven. Reddenings
  and distances for all five stars are estimated.

Title: The INT Photometric Hα Survey of the Northern Galactic Plane
    (IPHAS)
Authors: Drew, Janet E.; Greimel, R.; Irwin, M. J.; Aungwerojwit,
   A.; Barlow, M. J.; Corradi, R. L. M.; Drake, J. J.; Gänsicke,
   B. T.; Groot, P.; Hales, A.; Hopewell, E. C.; Irwin, J.; Knigge, C.;
   Leisy, P.; Lennon, D. J.; Mampaso, A.; Masheder, M. R. W.; Matsuura,
   M.; Morales-Rueda, L.; Morris, R. A. H.; Parker, Q. A.; Phillipps,
   S.; Rodriguez-Gil, P.; Roelofs, G.; Skillen, I.; Sokoloski, J. L.;
   Steeghs, D.; Unruh, Y. C.; Viironen, K.; Vink, J. S.; Walton, N. A.;
   Witham, A.; Wright, N.; Zijlstra, A. A.; Zurita, A.
Bibcode: 2005MNRAS.362..753D
Altcode: 2005MNRAS.tmp..738D; 2005astro.ph..6726D
  The Isaac Newton Telescope (INT) Photometric Hα Survey of the Northern
  Galactic Plane (IPHAS) is a 1800-deg<SUP>2</SUP> CCD survey of the
  northern Milky Way spanning the latitude range -5° &lt; b &lt; +
  5° and reaching down to r'~= 20 (10σ). Representative observations
  and an assessment of point-source data from IPHAS, now underway, are
  presented. The data obtained are Wide Field Camera images in the Hα
  narrow-band, and Sloan r' and i' broad-band filters. We simulate IPHAS
  (r'-Hα,r'-i') point-source colours using a spectrophotometric library
  of stellar spectra and available filter transmission profiles: this
  defines the expected colour properties of (i) solar metallicity stars,
  without Hα emission, and (ii) emission-line stars. Comparisons with
  observations of fields in Aquila show that the simulations of normal
  star colours reproduce the observations well for all spectral types
  earlier than M. A further comparison between colours synthesized
  from long-slit flux-calibrated spectra and IPHAS photometry for six
  objects in a Taurus field confirms the reliability of the pipeline
  calibration. Spectroscopic follow-up of a field in Cepheus shows that
  sources lying above the main stellar locus in the (r'- Hα,r'-i') plane
  are confirmed to be emission-line objects with very few failures. In
  this same field, examples of Hα deficit objects (a white dwarf and
  a carbon star) are shown to be readily distinguished by their IPHAS
  colours. The role IPHAS can play in studies of spatially resolved
  northern Galactic nebulae is discussed briefly and illustrated by a
  continuum-subtracted mosaic image of Shajn 147 (a supernova remnant,
  3° in diameter). The final catalogue of IPHAS point sources will
  contain photometry on about 80 million objects. Used on its own, or
  in combination with near-infrared photometric catalogues, IPHAS is a
  major resource for the study of stellar populations making up the disc
  of the Milky Way. The eventual yield of new northern emission-line
  objects from IPHAS is likely to be an order of magnitude increase on
  the number already known.

Title: Probing the circumstellar structures of T Tauri stars and
    their relationship to those of Herbig stars
Authors: Vink, Jorick S.; Drew, Janet E.; Harries, Tim J.; Oudmaijer,
   René D.; Unruh, Yvonne
Bibcode: 2005MNRAS.359.1049V
Altcode: 2005MNRAS.tmp..371V; 2005astro.ph..2535V
  We present Hα spectropolarimetry observations of a sample of 10 bright
  T Tauri stars, supplemented with new Herbig Ae/Be star data. A change in
  the linear polarization across Hα is detected in most of the T Tauri
  (9/10) and Herbig Ae (9/11) objects, which we interpret in terms of
  a compact source of line photons that is scattered off a rotating
  accretion disc. We find consistency between the position angle (PA)
  of the polarization and those of imaged disc PAs from infrared and
  millimetre imaging and interferometry studies, probing much larger
  scales. For the Herbig Ae stars AB Aur, MWC 480 and CQ Tau, we find
  the polarization PA to be perpendicular to the imaged disc, which is
  expected for single scattering. On the other hand, the polarization
  PA aligns with the outer disc PA for the T Tauri stars DR Tau and SU
  Aur and FU Ori, conforming to the case of multiple scattering. This
  difference can be explained if the inner discs of Herbig Ae stars
  are optically thin, whilst those around our T Tauri stars and FU
  Ori are optically thick. Furthermore, we develop a novel technique
  that combines known inclination angles and our recent Monte Carlo
  models to constrain the inner rim sizes of SU Aur, GW Ori, AB Aur
  and CQ Tau. Finally, we consider the connection of the inner disc
  structure with the orientation of the magnetic field in the foreground
  interstellar medium: for FU Ori and DR Tau, we infer an alignment of
  the stellar axis and the larger magnetic field direction.

Title: IPHAS: Surveying the North Galactic Plane in Hα
Authors: Drew, J. E.; Lennon, D. J., Greimel, R.; Zijlstra, A.;
   Irwin, J.; Aungwerowijt, A.; Barlow, M. J.; Corradi, R.; Evans,
   C. J.; Gaensicke, B.; Groot, P.; Hales, A.; Hopewell, E.; Irwin,
   M. J.; Jaigirdar, M.; Knigge, C.; Leisy, P.; Mampaso, A.; Matsuura,
   M.; Morales Rueda, L.; Morris, R.; Parker, Q. A.; Phillipps, S.;
   Rodríguez Gil, P.; Roelofs, G.; Skillen, I.; Steeghs, D.; Unruh,
   Y. C.; Viironen, K.; Vink, J.; Walton, N. A.; Witham, A.; Wright,
   N.; Zurita, A.
Bibcode: 2005INGN....9....3D
Altcode:
  H-alpha emission is ubiquitous in our Galaxy. It traces ionised gas of
  assorted nebulae such as HII regions, planetary nebulae, Wolf-Rayet
  nebulae, and supernova remnants. It is a strong signature of active
  stars, interacting binaries, very massive stars (especially supergiants,
  Luminous Blue Variables and Wolf-Rayet stars), Be stars, post-AGB stars,
  pre-main-sequence stars and so on. These objects represent important
  evolutionary phases which are generally short lived, and are hence
  few in number and difficult to find. Their discovery is therefore well
  worth the effort of a concerted programme and in August 2003 a major
  new survey project was started using the Wide Field Camera (WFC)
  on the Isaac Newton Telescope (INT) to do just that. It is called
  the INT Photometric H-alpha Survey of the Northern Galactic Plane,
  or IPHAS for short.

Title: IPHAS: The INT/WFC Photometric H-alpha Survey of the Northern
    Galactic Plane
Authors: Walton, N. A.; Drew, J.; Barlow, M. J.; Corradi, R.; Drake,
   J.; Gaensicke, B.; Greimel, R.; Groot, P.; Irwin, M. J.; Knigge,
   C.; Leisy, P.; Lennon, D. J.; Mampaso, A.; Masheder, M.; Morris,
   R.; Parker, Q. A.; Phillipps, S.; Pretorius, M.; Rodriguez-Gil,
   P.; Skillen, I.; Sokoloski, J.; Steegs, D.; Unruh, Y.; Witham, A.;
   Zijlstra, A.; Zurita, A.; IPHAS Collaboration
Bibcode: 2004AAS...20511303W
Altcode: 2004BAAS...36.1541W
  H-alpha emission both traces diffuse ionised nebulae and is commonly
  prominent in the spectra of pre- and post-main-sequence stars and
  interacting binaries. Since these are mostly relatively short-lived
  phases of evolution, they represent a minority of objects in a mature
  galaxy like our own at any one time. In the case of interacting
  binaries, they are simply hard to find. This scarcity, in turn, has
  acted as a brake on our understanding of these crucial evolutionary
  stages that, in youth, help shape the growth of planetary systems,
  and in old age, determine stellar end states along with the recycling
  of energy and chemically enriched matter back into the galactic
  environment. <P />IPHAS is our H-alpha survey of the Northern Galactic
  Plane being carried out with the 2.5-m Isaac Newton telescope's Wide
  Field Camera. Some ∼1800 deg<SUP>2</SUP> of the northern Galactic
  plane, over latitudes 5 &lt; b &lt; 5, is being imaged in H-alpha,
  r', i' to a depth of r' ∼20 mag. <P />Here we report on the first
  120 nights of observations. We comment on the advanced reduction
  pipeline employed to generate object catalogues. Early results are
  noted, including the discovery of a number of new, hitherto rare,
  quadropolar planetary nebulae. The IPHAS objects have been mined to
  select candidate samples for followup spectroscopic studies. Extreme
  emission line objects are selected from the (r' - H-alpha) v (r' - i')
  colour-colour plot. First detections of low mass young stars in the
  massive OB association Cyg OB2 are presented. <P />We note how this data
  set will be a valuable resource for the emerging Virtual Observatory,
  and will be especially powerful when compared with matching multi-colour
  IR and optical surveys (e.g. 2MASS and SDSS).

Title: Discovery of a WO star in the Scutum-Crux arm of the inner
    Galaxy
Authors: Drew, Janet E.; Barlow, M. J.; Unruh, Y. C.; Parker, Q. A.;
   Wesson, R.; Pierce, M. J.; Masheder, M. R. W.; Phillipps, S.
Bibcode: 2004MNRAS.351..206D
Altcode: 2004astro.ph..3482D
  We report the discovery of only the fourth massive WO star to be found
  in the Milky Way, and only the seventh identified within the Local
  Group. This has resulted from the first observations made in a programme
  of follow-up spectroscopy of candidate emission-line stars from the
  AAO/UKST Southern Galactic Plane Hα Survey. The optical spectrum of
  this star, to become WR 93b in the Catalogue of Galactic Wolf-Rayet
  stars, is presented and described. WR 93b is classified as WO3 and is
  shown to be highly reddened [E(B-V) = 2.1 +/- 0.1]. A recombination-line
  analysis of the emission lines yields the abundance ratios C/He = 0.95
  and O/He = 0.13 (by number). Comparisons at near-infrared wavelengths of
  reddening-corrected photometry between WR 93b and both of Sand 2 (WO3,
  D= 49 kpc) and Sand 5 (WO2, D= 1.75 kpc) yield a consistent distance
  to WR 93b of 3.4 kpc. Positioned at Galactic coordinates , the star is
  most likely located in the Scutum-Crux arm of the inner Milky Way. We
  note that none of the four Galactic WO stars lies significantly beyond
  the solar circle (with two well inside). <P />Estimation of the wind
  terminal velocity in WR 93b at 5750 km s<SUP>-1</SUP> makes this star
  the current wind-speed record holder among all non-degenerate stars.

Title: Multisite observations of SU Aurigae
Authors: Unruh, Y. C.; Donati, J. -F.; Oliveira, J. M.; Collier
   Cameron, A.; Catala, C.; Henrichs, H. F.; Johns-Krull, C. M.; Foing,
   B.; Hao, J.; Cao, H.; Landstreet, J. D.; Stempels, H. C.; de Jong,
   J. A.; Telting, J.; Walton, N.; Ehrenfreund, P.; Hatzes, A. P.;
   Neff, J. E.; Böhm, T.; Simon, T.; Kaper, L.; Strassmeier, K. G.;
   Granzer, Th.
Bibcode: 2004MNRAS.348.1301U
Altcode: 2004astro.ph..1081U
  We present results from the 1996 Multi-Site Continuous Spectroscopy
  (MUSICOS) campaign on the T Tauri star SU Aurigae. We find a 2.7-d
  periodicity in the HeI (587.6 nm) line, and somewhat longer, less
  well-pronounced periodicities in the Balmer lines and in Na D. Our
  observations support the suggestion that the wind and infall signatures
  are out of phase on SU Aur. We present Doppler images of SU Aur that
  have been obtained from least-squares deconvolved profiles. Images taken
  about one rotation apart show only limited overlap, in particular at low
  latitudes. This is due in part to limitations in signal-to-noise ratio,
  and in part to line-profile deformations that arise from short-lived
  and/or non-surface features. The agreement at high latitudes is better
  and suggests that at least some longer-lived features are present. The
  analysis of Stokes V profiles yields a marginal magnetic field detection
  during one of the phases.

Title: Spot sizes on Sun-like stars
Authors: Solanki, S. K.; Unruh, Y. C.
Bibcode: 2004MNRAS.348..307S
Altcode: 2003astro.ph.11310S
  The total area coverage by starspots is of interest for a variety
  of reasons, but direct techniques only provide estimates of this
  important quantity. Sunspot areas exhibit a lognormal size distribution
  irrespective of the phase of the activity cycle, implying that most
  sunspots are small. Here we explore the consequences if starspot areas
  were similarly distributed. The solar data allow for an increase in
  the fraction of larger sunspots with increasing activity. Taking
  this difference between the size distribution at sunspot maximum
  and minimum, we extrapolate to higher activity levels, assuming
  different dependences of the parameters of the lognormal distribution
  on total spot coverage. We find that, even for very heavily spotted
  (hypothetical) stars, a large fraction of the spots are smaller than
  the current resolution limit of Doppler images and hence might be
  missed on traditional Doppler maps.

Title: Specific Causes of Solar Cycle Irradiance Variability
Authors: Unruh, Y. C.
Bibcode: 2004cosp...35.4362U
Altcode: 2004cosp.meet.4362U
  The total solar irradiance has varied by about 0.1% between solar
  cycle minimum and maximum during the last couple of cycles. These
  variations are highly wavelength dependent with changes of an order of
  magnitude larger in the UV than in the visible. I discuss some of the
  proposed causes of total and spectral solar irradiance variability,
  and in particular the contribution of magnetic surface features.

Title: Resolved polarization changes across Hα  in the classical
    T Tauri star RY Tauri
Authors: Vink, Jorick S.; Drew, J. E.; Harries, T. J.; Oudmaijer,
   R. D.; Unruh, Y. C.
Bibcode: 2003A&A...406..703V
Altcode: 2003astro.ph..6095V
  We present linear Hα spectropolarimetry of the classical T Tauri
  star RY Tau. A change in the polarization percentage and position
  angle across Hα is detected, which suggests that line photons are
  scattered in a rotating disc. We derive the position angle from the
  slope of the loop in the (Q,U) diagram and find it to be 146 +/- 3
  degree. This is perpendicular to the position angle of the disc of 48
  +/- 5 degree as deduced from millimeter imaging by Koerner &amp; Sargent
  (\cite{Koerner1995}). This finding is consistent, as scattering off the
  imaged millimeter disc is expected to yield a polarization signature in
  a direction that is rotated by 90 degree from this disc. The observed
  spectropolarimetric behaviour of RY Tau is reminiscent of that seen
  in a large group of Herbig Ae stars, suggesting a common circumstellar
  origin of the polarized photons.

Title: Reconstruction of solar irradiance variations in cycle 23:
    Is solar surface magnetism the cause?
Authors: Krivova, N. A.; Solanki, S. K.; Fligge, M.; Unruh, Y. C.
Bibcode: 2003A&A...399L...1K
Altcode:
  A model of solar irradiance variations is presented which is based
  on the assumption that solar surface magnetism is responsible for all
  total irradiance changes on time scales of days to years. A time series
  of daily magnetograms and empirical models of the thermal structure
  of magnetic features (sunspots, faculae) are combined to reconstruct
  total (and spectral) irradiance from 1996 to 2002. Comparisons with
  observational data reveal an excellent correspondence, although the
  model only contains a single free parameter. This provides strong
  support for the hypothesis that solar irradiance variations are caused
  by changes in the amount and distribution of magnetic flux at the
  solar surface.

Title: Solar Variability and Climate Change; Poster Summary
Authors: Unruh, Y.
Bibcode: 2002EGSGA..27.6708U
Altcode:
  I will give a brief overview of the posters presented in session ST20
  and link them into the context of the talks presented. This will be
  complemented by my necessarily incomplete and personal selection of
  some poster highlights.

Title: Irradiance Medels based on Magnetic Activity
Authors: Solanki, S.; Krivova, N.; Unruh, Y.
Bibcode: 2002cosp...34E1357S
Altcode: 2002cosp.meetE1357S
  An introduction is given to the modelling of irradiance variations
  based on solar surface magnetism. We describe how a time series of daily
  magnetograms and empirical models of the thermal structure of magnetic
  features (sunspots, magnetic elements) are combined to reconstruct total
  and spectral irradiance on a time scale of weeks to years. Comparisons
  with observational data reveal an excellent correspondence. On a
  longer time scale of decades to centuries we first need to know how
  the Sun's magnetic field evolved. Hence reconstructions of the Sun's
  total magnetic flux are briefly introduced, before we present longer
  term reconstructions of the total and spectral irradiance since the
  Maunder minimum.

Title: The influence of an inclined rotation axis on solar irradiance
    variations
Authors: Knaack, R.; Fligge, M.; Solanki, S. K.; Unruh, Y. C.
Bibcode: 2001A&A...376.1080K
Altcode:
  Compared with Sun-like stars, the irradiance variations of the
  Sun over the solar cycle appear to be relatively small for its
  average activity level (Lockwood et al. \cite{Lockwood:etal:1992};
  Radick et al. \cite{Radick:etal:1998}). It has been proposed that
  the special position of Earth-based observers in the ecliptic plane
  may give the impression of a subdued solar photometric variability
  (Schatten \cite{Schatten:1993}). The aim of the present paper is to
  examine the influence on irradiance variations of a solar rotation
  axis inclined towards the observer. A three-component model is
  used to calculate relative flux variations of a given active-region
  distribution on the surface of the Sun as a function of inclination
  and wavelength. Wavelength-dependent intensity spectra are used to
  describe the contributions of the undisturbed photosphere, sunspots and
  faculae. The spectra result from models that have successfully been
  used to reproduce a host of solar data and thus represent realistic
  estimates of the radiative output from these solar features. We find
  that an inclined rotation axis increases the total solar irradiance
  variations maximally by 40%. The most probable value is approximately
  6%. This is much less than that suggested by former studies, which
  were based on simple contrast functions. In the averaged Strömgren
  filters we estimate a most probable increase of the solar variability
  of 30%. In addition, we estimate the dependence of the flux in the
  chromospheric Ca II H&amp;K lines on inclination. We find that the
  average chromospheric activity level depends only slightly on the
  inclination angle. The chromospheric variability of Sun-like stars,
  however, is significantly affected. Nonetheless, our results indicate
  that a different average inclination of stellar rotation axes relative
  to the observer cannot explain the discrepancy between the brightness
  variations of the Sun and Sun-like stars.

Title: Diagnostics from Spectral Irradiance Measurements
Authors: Unruh, Y. C.; Solanki, S. K.
Bibcode: 2001AGUSM..SP32B01U
Altcode:
  Solar irradiance varies in tune with solar activity. The irradiance
  changes show a strong wavelength dependence, being an order of magnitude
  larger in the UV than in the visible. The spectral dependence of the
  irradiance variations can be used to differentiate between mechanisms
  that may be responsible for the irradiance changes. I review some of
  the mechanisms that have been invoked in the past to explain the solar
  irradiance variations and compare their predicted spectral irradiance
  changes with solar irradiance measurements. The comparisons imply
  that surface magnetic features alone are sufficient to explain solar
  irradiance data.

Title: Stellar Irradiance Variations Caused by Magnetic Activity:
    The Influence of an Inclined Rotation Axis
Authors: Knaack, R.; Fligge, M.; Solanki, S. K.; Unruh, Y. C.
Bibcode: 2001ASPC..248..227K
Altcode: 2001mfah.conf..227K
  No abstract at ADS

Title: Are the Sun's Brightness Variations Really Tamer than Those of
Other Comparable Solar-type Stars? (CD-ROM Directory: contribs/unruh1)
Authors: Unruh, Y. C.; Knaack, R.; Fligge, M.; Solanki, S. K.
Bibcode: 2001ASPC..223..748U
Altcode: 2001csss...11..748U
  No abstract at ADS

Title: Doppler Images of LW Hydrae (CD-ROM Directory: contribs/unruh2)
Authors: Unruh, Y. C.; Gatti, A. A.; Drew, J. E.; Roberts, G.; van Wyk,
   F.; Marang, F.; Kilkenny, D.
Bibcode: 2001ASPC..223.1320U
Altcode: 2001csss...11.1320U
  No abstract at ADS

Title: Variations of the Solar Spectral Irradiance
Authors: Solanki, S. K.; Fligge, M.; Unruh, Y. C.
Bibcode: 2001IAUS..203...66S
Altcode:
  Not just the total solar irradiance is known to vary, but also the
  solar spectrum. Observations and models of solar spectral irradiance
  variations are presented.

Title: Preliminary MUSICOS 96 results on Balmer line variability on
    the T Tauri star SU aurigae
Authors: Oliveira, J. M.; Unruh, Y. C.; Foing, B. H.; MUSICOS 1996
   Collaboration
Bibcode: 2001AdSpR..26.1747O
Altcode:
  The study of young stellar objects is essential for the further
  understanding of the early evolutionary stages of the Sun and
  similar low-mass stars. In this context, T Tauri stars supply valuable
  information on their pre-main sequence evolution. SU Aur is a classical
  T Tauri star that shows little veiling and few emission lines. The
  Balmer line profiles are extremely variable, even on short time
  scales. We present results from the analysis of the variability of
  these spectral lines, based on a data set obtained during the world-wide
  multi-site spectroscopic MUSICOS 1996 campaign. We attempt to describe
  the interaction of the stellar magnetosphere and the accretion disk,
  and search for the signatures of mass inflow and ejection.

Title: Spectral Line Variability in the Circumstellar Environment
of the Classical T Tauri Star SU Aurigae (CD-ROM Directory:
    contribs/oliveira)
Authors: Oliveira, J. M.; Foing, B. H.; Unruh, Y. C.
Bibcode: 2001ASPC..223..539O
Altcode: 2001csss...11..539O
  No abstract at ADS

Title: Modelling solar irradiance variations: Comparison with
    observations, including line-ratio variations
Authors: Unruh, Y. C.; Solanki, S. K.; Fligge, M.
Bibcode: 2000SSRv...94..145U
Altcode:
  Solar irradiance variations show a strong temporal and spectral
  dependence. The progression of the Sun through its activity cycle as
  well as solar rotation are mirrored in the irradiance variations. The
  spectral dependence is such that the variations are several magnitudes
  larger in the EUV than in the visible or infrared. We present a simple
  3-component model that is based on the assumption that changes in
  the solar flux are exclusively due to changes in spot and facular
  coverage. We compare our model to observations of the spectral solar
  irradiance variations. Despite its simplicity, we find that the
  agreement between our model and the observations is surprisingly
  good. We also explore the reliability and the limitations of our
  approach by comparing observations of the solar facular contrast and
  of the changes in spectral line depths with our calculations.

Title: Modelling Short-Term Spectral Irradiance Variations
Authors: Fligge, M.; Solanki, S. K.; Unruh, Y. C.
Bibcode: 2000SSRv...94..139F
Altcode:
  On time-scales of the solar rotation most of the solar irradiance
  variations are caused by the changing distribution of solar surface
  magnetic features. We model these short-term irradiance variations
  using calculations of sunspot and facular contrasts as a function of
  wavelength and limb angle on the Sun. The position of active regions on
  the solar disc is derived from the MDI magnetograms. The reconstructed
  irradiance variations are compared with total and spectral irradiance
  measurements obtained by the VIRGO experiment on SOHO.

Title: Magnetospheric accretion and winds on the T Tauri star SU
    Aurigae. Multi-spectral line variability and cross-correlation
    analysis
Authors: Oliveira, J. M.; Foing, B. H.; van Loon, J. Th.; Unruh, Y. C.
Bibcode: 2000A&A...362..615O
Altcode: 2000astro.ph..9087O
  SU Aurigae is a T Tauri star that was well monitored during the MUSICOS
  96 multi-site campaign. We present the results of the spectroscopic
  analysis of the circumstellar environment of this star, particularly
  of the Hα , Hβ , Na I D and He I D3 line profiles. The signatures of
  modulated outflows and mass accretion events are analysed, as well as
  transient spectral features. We compute the cross-correlation function
  (CCF) of several pairs of (velocity bins in) spectral lines to better
  investigate the profiles' temporal variability. We found increasing
  time lags between the variability of He I D3, Na I D and Hβ . We
  propose this may be understood in terms of azimuthal distortion of the
  magnetic field lines due to the different rotation rates of the star
  and the disk. We find the slightly blueshifted absorption features in
  Hα , Hβ \ and Na I D to be anti-correlated with the accretion flow
  signatures. We propose that the transient absorption features in the
  blue wings of Hα , Hβ \ and Na I D (signatures of mass outflows),
  and flare brightenings are related to the disruption of distorted
  magnetospheric field lines. Based on observations obtained during the
  MUSICOS~96 campaign in which were involved: Isaac Newton Telescope
  (INT, La Palma), Observatoire de Haute Provence (OHP, France), McDonald
  Observatory (MDO, USA), Beijing Astronomical Observatory (BAO, Xinglong,
  China) and Canada-France-Hawaii Telescope (CFHT, Hawaii).

Title: Modelling irradiance variations from the surface distribution
    of the solar magnetic field
Authors: Fligge, M.; Solanki, S. K.; Unruh, Y. C.
Bibcode: 2000A&A...353..380F
Altcode:
  An important question in solar physics is to what extent solar surface
  magnetism affects the solar irradiance. Previous attempts to answer this
  question have employed proxies of the magnetic field to reconstruct the
  irradiance and compare it with observations. Here we present the first
  model calculations of solar irradiance variations based on variations
  of the surface distribution of the solar magnetic field. The irradiance
  reconstruction makes use of sunspot and facular contrasts calculated
  as a function of wavelength and limb angle on the Sun. The position
  and size of magnetic features on the solar disk are extracted from
  full-disk magnetograms obtained by the Michelson Doppler Interferometer
  (MDI) onboard the SOHO spacecraft. The reconstructed spectral irradiance
  variations are compared with total and spectral contrast measurements
  obtained by the VIRGO instrument onboard SOHO. Our reconstructions are
  able to reproduce variations on the time-scale of the solar rotation
  with much greater accuracy than previous models based on disk-integrated
  magnetic proxies.

Title: The influence of an inclined rotation axis on solar irradiance
    variations
Authors: Knaack, R.; Fligge, M.; Solanki, S. K.; Unruh, Y. C.
Bibcode: 2000ssls.work...45K
Altcode:
  The irradiance variations of the Sun over the solar cycle are relatively
  small compared with sun-like stars (Radick et al., 1998). It has been
  proposed that a random distribution of stellar rotation axes relative to
  the ecliptic plane could explain their larger variability (Schatten,
  1993). We examine the influence on total irradiance variations of
  the inclination of the solar rotation axis relative to an observer. A
  three-component model is used to calculate the relative flux variations
  of a given distribution of active regions on the surface of the Sun as
  a function of the inclination. One component is the quiet Sun, another
  is a sunspot component and the third describes the faculae. We find
  that the inclination effect increases the total irradiance variations
  of the Sun maximally by 40%. The most probable value is approximately
  5%. This is much less than former studies (Schatten, 1993, Radick et
  al., 1998) suggested.

Title: Solar Surface Magnetism and the Increase of Solar Irradiance
    between Activity Minimum and Maximum
Authors: Fligge, M.; Solanki, Sami K.; Meunier, Nadege; Unruh,
   Yvonne C.
Bibcode: 2000ESASP.463..117F
Altcode: 2000sctc.proc..117F
  No abstract at ADS

Title: Modelling Solar Irradiance Variations: Comparison with
    Observations, Including Line-Ratio Variations
Authors: Unruh, Y. C.; Solanki, S. K.; Fligge, M.
Bibcode: 2000svc..book..145U
Altcode:
  No abstract at ADS

Title: Modelling Short-Term Spectral Irradiance Variations
Authors: Fligge, M.; Solanki, S. K.; Unruh, Y. C.
Bibcode: 2000svc..book..139F
Altcode:
  No abstract at ADS

Title: Spectral Line Variability in the Circumstellar Environment
    of the Classic al T Tauri Star SU Aurigae
Authors: Oliveira, J. M.; Foing, B. H.; Unruh, Y. C.
Bibcode: 1999astro.ph.12199O
Altcode:
  SU Aurigae is a classical T Tauri star of spectral type G2. This star
  was one of the scientific targets of the MUSICOS 96 multi-site campaign
  that provided a wealth of high resolution cross-dispersed spectral data
  with a good continuous time coverage. We present the results of the
  analysis of the complex circumstellar environment of this star, with
  particular regard to magnetospheric models, in which the accretion from
  the disk is channelled onto the star along magnetic field lines. The
  signatures of modulated outflows and mass accretion events are present
  in the spectra, as well as transient spectral features. We computed
  auto-correlation and cross-correlation functions to better investigate
  the source of the profiles' variability. The comparison of the profiles
  of different spectral lines allows us to study the footprints of events
  effectively observed at different distances from the stellar surface.

Title: Coronal emission and dynamo saturation
Authors: Jardine, M.; Unruh, Y. C.
Bibcode: 1999A&A...346..883J
Altcode:
  We show that the observed saturation of X-ray emission with increasing
  rotation rate in solar-type stars does not necessarily imply saturation
  of the underlying dynamo. This effect can be caused by the centrifugal
  stripping of the corona. As the stellar rotation rate is increased,
  centrifugal forces cause a rise in the pressure and density in the outer
  parts of the largest magnetic loops. This may explain the observed
  formation of large prominences close to the co-rotation radius where
  centrifugal forces begin to dominate over gravity. In order for these
  massive prominences to be contained against centrifugal ejection, the
  coronal magnetic field must be highly stressed and must be evolving
  on a timescale of a few days as determined by the observed prominence
  lifetime. We postulate that the co-rotation radius marks the position
  at which the corona becomes distorted by centrifugal forces. As the
  stellar rotation rate is increased, the co-rotation radius moves closer
  to the surface, reducing the extent of the ``undisturbed'' corona. We
  take as illustrative examples two simple field topologies and show
  that if the X-ray emission comes only from this undisturbed volume,
  then a saturation of the X-ray emission with increasing rotation rate
  occurs naturally. This effect may mimic true dynamo saturation or
  disguise its onset.

Title: Short-term spectroscopic variability in the pre-main sequence
    Herbig AE star AB Aurigae during the MUSICOS 96 campaign
Authors: Catala, C.; Donati, J. F.; Böhm, T.; Landstreet, J.;
   Henrichs, H. F.; Unruh, Y.; Hao, J.; Collier Cameron, A.; Johns-Krull,
   C. M.; Kaper, L.; Simon, T.; Foing, B. H.; Cao, H.; Ehrenfreund, P.;
   Hatzes, A. P.; Huang, L.; de Jong, J. A.; Kennelly, E. J.; ten Kulve,
   E.; Mulliss, C. L.; Neff, J. E.; Oliveira, J. M.; Schrijvers, C.;
   Stempels, H. C.; Telting, J. H.; Walton, N.; Yang, D.
Bibcode: 1999A&A...345..884C
Altcode:
  We present results of the spectroscopic monitoring of AB Aur obtained
  during the MUSICOS 96 campaign. The analysis is mainly focussed on the
  He I D3 line, on the Hα line, and on a set of photospheric lines. The
  star was monitored irregularly for more than 200 hours. We confirm
  the high level of variability of spectral lines in AB Aur. We find
  that the photospheric lines have a profile differing significantly
  from a classical rotational profile. The dominant features of this
  abnormal photospheric profile are a blue component, in absorption, whose
  velocity is modulated with a 34hr period, and a red component, stable
  in velocity but of variable intensity, with a possible periodicity
  near 43 hrs. The He I D3 line exhibits two well-defined components:
  a blue component, always in emission with a velocity modulated with a
  45hr period, and a red component of variable intensity, alternatively
  in emission and in absorption, occurring at a fixed velocity, with a
  variable intensity possibly modulated with a 45 hr period. The Hα line,
  showing a P Cygni profile, also exhibits pseudo-periodic variations
  of its blue absorption component, but its variability appears more
  complicated than that of the other lines studied here. We suggest
  that the blue component of the photospheric lines is modulated by the
  star's rotation, with a period of 34 hrs, due to a highly inhomogeneous
  photosphere, involving significant radial flows. Our model also involves
  downflows onto the stellar pole to account for the red components of the
  photospheric lines and of the He I D3 line. We propose two different
  interpretations of the behavior of the blue component of the He I D3
  line. In the first one, this component is formed in a wind originating
  from the star's equatorial regions. In this interpretation, the rotation
  period of the equatorial regions of the star is 45 hrs, implying a 25%
  surface differential rotation, with the pole rotating faster than the
  equator. The second interpretation involves a wind originating from
  a region of a circumstellar disk, at a distance of 1.6 stellar radii
  from the star's center, with a rotation period of 45 hrs. We are not
  able to decide which one of these two interpretations is more likely,
  on the basis of the data presented here. Based on observations obtained
  during the MUSICOS 96 MUlti-SIte COntinuous Spectroscopic campaign,
  collected at the Canada-France Hawaii, the McDonald 2.1m, the La
  Palma 2.5m Isaak Newton, the Observatoire de Haute-Provence 1.93m,
  the Xinglong 2.16m, and the Ritter Observatory 1m telescopes

Title: Optical and ultraviolet observations of a strong flare in
    the young, single K2 dwarf LQ Hya
Authors: Montes, D.; Saar, S. H.; Collier Cameron, A.; Unruh, Y. C.
Bibcode: 1999MNRAS.305...45M
Altcode: 1998astro.ph.11452M
  We present high-resolution optical echelle spectra and IUE observations
  during a strong flare on 1993 December 22 in the very active, young,
  rapidly rotating, single K2 dwarf LQ Hya. The initial impulsive
  phase of the flare, which started sometime between 2:42 ut and 4:07
  ut, was characterized by strong optical continuum enhancement and
  blueshifted emission lines with broad wings. The optical chromospheric
  lines reached their maximum intensity at ~ 5:31 ut, by which time the
  blueshift vanished and the optical continuum enhancement had sharply
  decreased. Thereafter, the line emission slowly decreased and the lines
  redshift in a gradual phase that lasted at least two more hours. The
  Mg II lines behaved similarly. Quiescent C IV flux levels were not
  recovered until 21 h later, though a data gap and a possible second
  flare make the interpretation uncertain. In addition to the typically
  flare-enhanced emission lines (e.g., H alpha and H beta), we observe
  He I D_3 going into emission, plus excess emission (after subtraction
  of the quiescent spectrum) in other He I and several strong neutral
  metal lines (e.g., Mg I b). Flare enhancement of the far-ultraviolet
  continuum generally agrees with an Si I recombination model. We
  estimate the total flare energy, and discuss the broad components,
  asymmetries and Doppler shifts seen in some of the emission lines.

Title: The spectral dependence of facular contrast and solar
    irradiance variations
Authors: Unruh, Y. C.; Solanki, S. K.; Fligge, M.
Bibcode: 1999A&A...345..635U
Altcode:
  We present model calculations of facular and sunspot contrasts as a
  function of wavelength and limb angle on the Sun. These are the first
  such calculations; they assume LTE and are based on opacity distribution
  functions (ODFs). The calculated facular contrasts as a function of
  limb angle fit into the general picture of contrast measurements,
  and the behaviour of the contrast with wavelength at a given limb
  angle is in excellent agreement with the measurements. The calculated
  intensity spectra are used to construct the solar flux spectrum for
  different levels of solar activity. It is assumed that the irradiance
  or flux variations are due to changes in the sunspot and facular
  filling factors. The model atmosphere used to calculate the facular
  intensities has been tuned so that the calculated irradiance variations
  match the observed total and spectral irradiance variations during
  the last solar cycles. The model calculations have also been used
  to estimate the relative importance of continuum and spectral-line
  variations in producing irradiance variations. The results suggest
  that the continuum variations only contribute negligibly to the total
  irradiance variations on solar-cycle time scales.

Title: Latitude distributions and lifetimes of star-spots on G dwarfs
    in the alpha Persei cluster
Authors: Barnes, J. R.; Collier Cameron, A.; Unruh, Y. C.; Donati,
   J. F.; Hussain, G. A. J.
Bibcode: 1998MNRAS.299..904B
Altcode:
  We present a set of maximum-entropy reconstructions of the star-spot
  distributions on two rapidly rotating G dwarfs in the alpha Persei
  cluster, from spectra taken at the William Herschel Telescope on
  three nights in 1996 October and November. Since these stars are too
  faint for conventional Doppler imaging, which makes use of only one
  or a few lines, we take the large number of photospheric metal lines
  available in an echelle spectrum, and deconvolve them into a single,
  high signal-to-noise ratio profile. We show that this technique results
  in a typical multiplex gain of 22.5 in signal-to-noise ratio for a
  given spectrum, the equivalent of using a single line obtained on
  a 63-m telescope. The image reconstructions demonstrate that both
  these stars have cool high-latitude regions or polar crowns, and
  low-latitude features, in contradiction to the suggestion that only
  high-latitude spots should be present. Cross-correlation between image
  reconstructions of He 699, 31 days apart, reveals a lack of correlation
  between detailed small-scale structures. This places an upper limit
  for the lifetime of the observed features at less than one month. The
  Hα profiles are also found to exhibit absorption features indicating
  the presence of prominence clouds, at or below the corotation radius.

Title: A model of solar total and spectral irradiance variations
Authors: Fligge, M.; Solanki, S. K.; Unruh, Y. C.; Froehlich, C.;
   Wehrli, Ch.
Bibcode: 1998A&A...335..709F
Altcode:
  We model solar spectral irradiance variations under the assumption
  that they are produced by sunspots and faculae alone. The model is
  based on three components, i.e. quiet Sun, assumed to be temporally
  invariant, sunspots and faculae whose temporal variations are mimicked
  using time series of sunspot areas and Mg II core-to-wing ratios. The
  detailed flux spectrum for each component is employed. The results
  are compared to spectral irradiance measurements at 402 nm, 500 nm
  and 862 nm obtained between February 22 and December 31, 1996 by
  the three-channel sunphotometers (SPM) which are part of the VIRGO
  package onboard SOHO. Our model shows a good correlation with the
  measured variations of the three colour channels and of the total
  irradiance. Since it also successfully reproduces changes in the UV
  spectral irradiance, irradiance variations and observed variations
  of the faculae-to-spots filling factor ratio since 1978, our model
  supports earlier suggestions that a large part of the solar irradiance
  variations is caused by magnetic fields at the solar surface. Finally,
  we use the model to test whether the difference between the magnitude
  of solar and stellar brightness variations reported by Lockwood et
  al. (1992) is due to the particular filters they use for their stellar
  observations. Our results suggest that this effect can explain only
  a small part of the discrepancy.

Title: Surface inhomogeneities and line variability on DF Tau
Authors: Unruh, Y. C.; Collier Cameron, A.; Guenther, E.
Bibcode: 1998MNRAS.295..781U
Altcode:
  We have mapped surface inhomogeneities on the classical T Tauri star DF
  Tau, using the Lii doublet at 670.8 nm, the Cai lines at 612.2 nm and
  643.9 nm and a calcium and iron blend at 646.3 nm. We find compelling
  evidence that there are hotspots with temperatures of more than 5000
  K. Two of the hotspots produce line-profile deformations that can
  be traced as they move through the cross-correlated profiles. When
  one of the hotspots crosses the stellar disc, redshifted absorption
  components appear in the Na D lines. As these redshifted absorption
  features are usually tracers for mass-infall we interpret this hotspot
  as an accretion shock close to the stellar surface. Parts of the surface
  of DF Tau are covered with a hot chromosphere that is visible in the
  Caii infrared triplet lines and the narrow component of Hei. We find
  no correlation between the veiling and the lines that originate from
  the hot chromosphere, suggesting that the veiling and the chromospheric
  emission are produced in physically distinct regions.

Title: Prominences on Rapidly-Rotating Solar-Type Stars
Authors: Jardine, M.; Barnes, J.; Unruh, Y.; Collier Cameron, A.
Bibcode: 1998ASPC..150..235J
Altcode: 1998npsp.conf..235J; 1998IAUCo.167..235J
  No abstract at ADS

Title: MUSICOS Observations of SU AUR
Authors: Unruh, Yvonne C.; Donati, J. -F.; Balona, L.; Bohm, T.;
   Cao, H.; Catala, C.; Collier Cameron, A.; Ehrenfreund, P.; Foing,
   B.; Granzer, T.; Hao, J.; Hatzes, A.; Henrichs, H.; Johns-Krull,
   C.; de Jong, J.; Kennelly, T.; Landstreet, J.; Morrison, N.; Mullis,
   C.; Neff, J.; Oliveira, J.; Schrijvers, C.; Simon, T.; Stempels, E.;
   Strassmeier, K. G.; Telting, J.; Walton, N.
Bibcode: 1998ASPC..154.2064U
Altcode: 1998csss...10.2064U
  We present first results of the high-resolution observations of SU Aur
  obtained through the MUSICOS network in 1996 Nov. The data set is unique
  in that it gives us complete phase coverage for almost two rotation
  periods of SU Aur. This is particularly valuable for T Tauri stars as
  they can vary dramatically on the time scale of one rotation period.

Title: A model of the wavelength dependence of solar irradiance
    variations
Authors: Solanki, S. K.; Unruh, Y. C.
Bibcode: 1998A&A...329..747S
Altcode:
  The variation of the solar irradiance over the solar cycle has a strong
  wavelength dependence, being larger at shorter wavelengths. Here
  we present simple models of the spectral dependence of irradiance
  variations between solar activity maximum and minimum. We find that the
  observations (which concentrate on the UV) cannot be reproduced by a
  change in effective temperature of the Sun (or of parts of its surface)
  alone. We can, however, reproduce the data with either a 2-component or
  a 3-component model, of which one component is the quiet Sun, another
  is a facular component, and the third (in the case of the 3-component
  model) represents the temperature stratification of sunspots. The
  facular component is found to be very close to the facular models F
  or P of Fontenla et al. (1993). The success of these models supports
  the assumption underlying many studies of total solar irradiance
  variations that these are caused mainly by magnetic fields at the solar
  surface. Our investigation also allows an improved estimate of the
  relative contribution of the various layers in the solar photosphere and
  of the different wavelength regions to the total irradiance variations.

Title: The Wavelength Dependence of Solar Irradiance Variations
Authors: Unruh, Yvonne C.; Solanki, Sami K.
Bibcode: 1998ASPC..154..700U
Altcode: 1998csss...10..700U
  The observed irradiance variations over a solar cycle show a strong
  wavelength dependence; the variations are strongest in the UV and
  very weak in the visible. Here we present a simple model of the
  spectral dependence of the solar irradiance. We can exclude models that
  postulate a change in the effective temperature of the Sun or of parts
  of the Sun. However, we find that the observed irradiance variations
  can be matched with a model that includes the different temperature
  stratification of the quiet photosphere, the faculae and the sunspots.

Title: MUSICOS Observations of SU Aurigae
Authors: Unruh, Y. C.; Donati, J. -F.; et al.
Bibcode: 1998cvsw.conf..355U
Altcode:
  No abstract at ADS

Title: A Strong Flare on the K Dwarf LQ Hya
Authors: Montes, D.; Saar, S. H.; Collier Cameron, A.; Unruh, Y. C.
Bibcode: 1998ASPC..154.1508M
Altcode: 1998csss...10.1508M
  We present high resolution optical echelle spectra and IUE SWP
  observations during a strong flare on 1993 December 22 in the very
  active, young, rapidly rotating, single K2 dwarf LQ Hya. The temporal
  evolution of the flare consists of an initial impulsive phase,
  characterized by strong continuum enhancement, which started between
  02:42 UT (quiescent spectrum) and 04:36 UT (first spectrum with a strong
  increase in the chromospheric lines). The chromospheric lines reached
  their maximum intensity ~55 min later, by which time the continuum
  enhancement had sharply decreased. Thereafter, the line emission slowly
  decreased in a gradual phase that lasted at least until the end of
  the observation (07:29 UT). IUE data indicate that quiescent C iv flux
  levels were not recovered after ~4 UT on the following day. We describe
  the variation of the continuum enhancement, the optical and the UV lines
  during the flare. In addition to the emission lines that show strong
  flare enhancement (e.g., Hα and Hβ), we observe He i D<SUB>3</SUB>
  going into emission. After subtraction of the quiescent spectrum,
  we also observe excess emission in He i lines at 4921.9, 5015.7, and
  6678.1AA, and in other metal lines such as the Na i D<SUB>1</SUB> and
  D<SUB>2</SUB>, the Mg i b triplet and several Fe i and Fe ii lines. We
  estimate the energy release during the flare, and analyze the broad
  components and asymmetries seen in some of the emission lines.

Title: Balmer Line Profiles Variations in SU Aurigae from the MUSICOS
    96 Multi-site Campaign
Authors: Oliveira, J. M.; Unruh, Y. C.; Foing, B. H.; MUSICOS 96
   Collaboration
Bibcode: 1998Ap&SS.261..143O
Altcode: 1999Ap&SS.261..143O
  No abstract at ADS

Title: Modelling Spectral Irradiance Variations obtained by VIRGO
Authors: Fligge, M.; Solanki, S. K.; Unruh, Y.; Frohlich, C.;
   Wehrli, Ch.
Bibcode: 1998ASPC..140..311F
Altcode: 1998ssp..conf..311F
  No abstract at ADS

Title: Wavelength Dependence of Solar Irradiance Variability from
    VIRGO Onboard SOHO
Authors: Wehrli, C.; Fröhlich, C.; Anklin, M.; Fligge, M.; SOlanki,
   S. K.; Unruh, Y.
Bibcode: 1997ESASP.415..497W
Altcode: 1997cpsh.conf..497W
  No abstract at ADS

Title: Does chromospheric emission mimic polar starspots in Doppler
    images?
Authors: Unruh, Y. C.; Collier Cameron, A.
Bibcode: 1997MNRAS.290L..37U
Altcode:
  We have used time-series spectra of the sodium doublet at 589.0 and
  589.6nm in AB Doradus to investigate the effects of a chromospheric
  temperature rise on Doppler images derived from strong lines whose
  cores are formed in the upper photosphere and lower chromosphere. On
  solar-type stars, the NaD lines probe a range of heights and tend
  to be much more sensitive to the chromospheric temperature structure
  than the weaker photospheric lines that are commonly used for Doppler
  imaging. Contrary to suggestions that polar spots may be an artefact
  arising from chromospheric emission reversals, we find that the images
  obtained from the NaD lines show less high-latitude structure, and give
  more reliable light-curve predictions, than images derived previously
  from fits to several weaker photospheric lines.

Title: Doppler imaging of AB Doradus using the Lii 6708 line
Authors: Hussain, G. A. J.; Unruh, Y. C.; Collier Cameron, A.
Bibcode: 1997MNRAS.288..343H
Altcode:
  We present maximum entropy reconstructions of the stellar surface
  of the K0 dwarf AB Doradus using observations obtained in 1993
  November. Doppler images are produced using the Lii 6708-Angstroms line
  and compared to images produced using Cai and Fei lines. An Li abundance
  of log N(Li) = 2.9 +/- 0.3 is measured using local thermodynamic
  equilibrium (LTE) profile synthesis. By assessing how enhanced spot
  Li abundances affect fits between synthetic reconstructions and the
  observed data, we conclude that the presence of starspots is unlikely to
  lead to an overestimation of the photospheric Li abundance. Moreover,
  Li abundances in starspots do not appear to be enhanced with respect
  to the photospheric level. The equivalent width measurements for
  the Lii 6708-Angstroms line are strengthened by the presence of
  starspots. This effect is probably due to their lower effective
  temperatures. Because the spots were widely distributed in longitude
  at the time of observation, the extent to which the Lii line equivalent
  width is modulated as the star rotates is diluted.

Title: Magnetic loops on rapidly rotating stars.
Authors: Unruh, Y. C.; Jardine, M.
Bibcode: 1997A&A...321..177U
Altcode:
  We present models for the thermal and mechanical equilibria of slender
  magnetic loops on rapidly-rotating stars. These loops are embedded
  within an arcade located on the stellar equator. The loop properties
  are governed principally by the specified base pressure and conductive
  flux. While rapid rotation is important in determining the pressure
  structure within the loop, its main effect on the loop shape is through
  its influence on the base values of magnetic field strength, pressure,
  and conductive flux. We have compared our models with observations of
  the temperatures and X-ray fluxes of stars with a range of rotation
  rates. By using the observed variation of the differential emission
  measure with rotation rate {OMEGA} and allowing the base magnetic
  field strength to scale as B {prop.to}{OMEGA}^q^ (q=0.5,0.75,1.0)
  we can explain the variation of the temperature and X-ray flux of the
  slower rotators. For the most rapid rotators, however (approximately
  {OMEGA}/{OMEGA}<SUB>sun</SUB>_&gt;10) it appears that a single value of
  q for all rotation rates cannot explain the observations and some other
  mechanism is needed to explain the saturation in the X-ray flux. We
  have also investigated the effect of using a heating function that is
  proportional to the density and one that falls off exponentially with
  height. With the parameters that we can calculate from these models
  it is not possible to discriminate between these two types of heating.

Title: Reliability tests for Doppler imaging
Authors: Unruh, Y. C.
Bibcode: 1996IAUS..176...35U
Altcode:
  No abstract at ADS

Title: The Evolution of Surface Structures on Ab-Doradus
Authors: Unruh, Y. C.; Collier Cameron, A.; Cutispoto, G.
Bibcode: 1995MNRAS.277.1145U
Altcode:
  We present the third set of a long-term series of Doppler images of
  the starspot distribution on AB Doradus, a rapidly rotating active
  K0 dwarf. The images were obtained from simultaneous spectroscopic
  and photometric observations taken on the Anglo-Australian Telescope
  and the European Southern Observatory in 1993 November. Our images
  show two active latitudes, a low-latitude band producing most of the
  photometric modulation, and a high-latitude band centred at 60°. The
  spot distribution at low latitudes is very stable and persists over 5
  stellar rotations. It is also remarkably similar to the distribution
  found in 1992 December. The high-latitude structure is more variable
  and seems to change on the order of a few rotation periods. In
  agreement with measurements from 1992 January, we find no indication
  for differential rotation on AB Doradus.

Title: The sensitivity of Doppler imaging to line profile models
Authors: Unruh, Y. C.; Collier Cameron, A.
Bibcode: 1995MNRAS.273....1U
Altcode:
  In recent years there have been a number of successful reconstructions
  of the surfaces of fast rotating stars using Doppler imaging. As a
  large proportion of the imaged stars show large high-latitude spots,
  some doubt remains as to whether these high-latitude spots might be
  artefacts. In this paper we investigate how sensitive Doppler imaging
  is to the exact shape of the mapping line profile and its variation as
  a function of limb angle. We find that Doppler imaging is surprisingly
  robust against errors in the limb dependence of the profile, but that
  errors in the shape of the profile, and in particular the neglect of
  blends at considerable distances from the mapping line, will lead to
  spurious banding in the reconstructed images.

Title: Surface structures on young solar-type stars.
Authors: Collier Cameron, A.; Unruh, Y. C.
Bibcode: 1995mscs.conf..201C
Altcode:
  No abstract at ADS

Title: Surface structure on DF Tau
Authors: Unruh, Y. C.; Collier-Cameron, A.; Guenther, E.
Bibcode: 1995IAUS..176P..93U
Altcode:
  No abstract at ADS

Title: Doppler images of AB Doradus in 1992 January.
Authors: Collier Cameron, A.; Unruh, Y. C.
Bibcode: 1994MNRAS.269..814C
Altcode:
  We present a set of maximum entropy reconstructions of the starspot
  distribution on the surface of the rapidly rotating KO dwarf AB
  Doradus. The images were obtained from three independent data
  sets secured on three consecutive nights of observation at the
  Anglo-Australian Telescope in 1992 January. We discuss the effects of
  several potential types of systematic error in Doppler imaging, and
  methods of eliminating them. Independent reconstructions are presented
  in the three photo spheric lines: Ca I 643.9 nm, Fe I 666.3 nm and Ca
  I 671.8 nm. All the images indicate a bimodal latitude distribution of
  spot area coverage, with a broad low-latitude band and a circumpolar
  `crown'. The gross azimuthal structures in the polar crown and the
  low-latitude band show no evidence of longitude shifts over the
  duration of the observing run. On the time-scale of a single stellar
  rotation the star's surface layers thus appear to be in a state of
  nearly solid-body rotation. Key words: techniques: image processing -
  stars: activity - stars: atmospheres - stars: individual: AB Dor -
  stars: magnetic fields - stars: rotation.

Title: Doppler imaging of late-type stars
Authors: Unruh, Y. C.
Bibcode: 1994PhDT........12U
Altcode:
  No abstract at ADS

Title: The Sensitivity of Doppler Imaging to Errors in the Line
    Profile Shape
Authors: Unruh, Yvonne C.; Collier Cameron, Andrew
Bibcode: 1994ASPC...64..667U
Altcode: 1994csss....8..667U
  No abstract at ADS

Title: Doppler imaging of late-type stars
Authors: Unruh, Yvonne Christine
Bibcode: 1994PhDT........15U
Altcode:
  No abstract at ADS

Title: Photospheric inhomogeneities on cool stars
Authors: Collier Cameron, A.; Jeffery, C. S.; Unruh, Y. C.
Bibcode: 1992sccw.conf...81C
Altcode:
  No abstract at ADS

