J/A+A/615/A139ivo://CDS.VizieR/J/A+A/615/A139doi:10.26093/cds/vizier.36150139CDSAmarsi A.M.Nordlander T.Barklem P.S.Asplund M.Collet R.Lind K.2018-09-25T13:18:25Z2018-07-27T08:30:59ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frastronomical-modelsstellar-atmospheresspectroscopyeffective-temperaturelate-type-starsHydrogen Balmer lines are commonly used as spectroscopic effective temperature diagnostics of late-type stars. However, reliable inferences require accurate model spectra, and the absolute accuracy of classical methods that are based on one-dimensional (1D) hydrostatic model atmospheres and local thermodynamic equilibrium (LTE) is still unclear. To investigate this, we carry out 3D non-LTE calculations for the Balmer lines, performed, for the first time, over an extensive grid of 3D hydrodynamic STAGGER model atmospheres. For H{alpha}, H{beta}, and H{gamma} we find significant 1D non-LTE versus 3D non-LTE differences (3D effects): the outer wings tend to be stronger in 3D models, particularly for H{gamma}, while the inner wings can be weaker in 3D models, particularly for H{alpha}. For H{alpha}, we also find significant 3D LTE versus 3D non-LTE differences (non-LTE effects): in warmer stars (Teff~~6500K) the inner wings tend to be weaker in non-LTE models, while at lower effective temperatures (Teff~~4500K) the inner wings can be stronger in non-LTE models; the non-LTE effects are more severe at lower metallicities. We test our 3D non-LTE models against observations of well-studied benchmark stars. For the Sun, we infer concordant effective temperatures from H{alpha}, H{beta}, and H{gamma}; however the value is too low by around 50K which could signal residual modelling shortcomings. For other benchmark stars, our 3D non-LTE models generally reproduce the effective temperatures to within 1{sigma} uncertainties. For H{alpha}, the absolute 3D effects and non-LTE effects can separately reach around 100K, in terms of inferred effective temperatures. For metal-poor turn-off stars, 1D LTE models of H{alpha} can underestimate effective temperatures by around 150K. Our 3D non-LTE model spectra are publicly available, and can be used for more reliable spectroscopic effective temperature determinations.2018A&A...615A.139Ahttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/615/A139CatalogResearchIsServedByTAP VizieR generic servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/615/A139https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/615/A139http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/615/A139https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/615/A139https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/615/A139http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/615/A139GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapdefaultJ/A+A/615/A139/lineprofRaw line profilesrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintTeffEffective temperatureKphys.temperature.effectiveintloggBase 10 logarithm of surface gravitylog(cm.s**-2)phys.gravityfloat[Fe/H]Iron abundancephys.abund.FefloatnuFrequencyHzem.freqdoublewlVacuum wavelengthnmem.wldoublewlairAir wavelengthnmem.wldoublemuViewing anglesrc.orbital.inclinationdoublewmuViewing angle weightsrc.orbital.inclinationdoubleIcContinuum intensityW.m**-1.Hz**-1spect.line.intensitydoubleIIntensityW.m**-1.Hz**-1spect.line.intensitydouble