3D non-LTE Balmer line formation Virtual Observatory Resource

Authors
  1. Amarsi A.M.
  2. Nordlander T.
  3. Barklem P.S.
  4. Asplund M.
  5. Collet R.
  6. Lind K.
  7. Published by
    CDS
Abstract

Hydrogen 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.

Keywords
  1. Astronomical models
  2. Stellar atmospheres
  3. Spectroscopy
  4. Effective temperature
  5. Late-type stars
Bibliographic source Bibcode
2018A&A...615A.139A
See also HTML
https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/615/A139
IVOA Identifier IVOID
ivo://CDS.VizieR/J/A+A/615/A139
Document Object Identifer DOI
doi:10.26093/cds/vizier.36150139

Access

Web browser access HTML
http://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/615/A139
https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/615/A139
http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/615/A139
IVOA Table Access TAP
http://tapvizier.cds.unistra.fr/TAPVizieR/tap
Run SQL-like queries with TAP-enabled clients (e.g., TOPCAT).

History

2018-07-27T08:30:59Z
Resource record created
2018-07-27T08:30:59Z
Created
2018-09-25T13:18:25Z
Updated

Contact

Name
CDS support team
Postal Address
CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France
E-Mail
cds-question@unistra.fr