Lyman α wing absorption in cool white dwarf stars

Kowalski & Saumon identified the missing absorption mechanism in the observed spectra of cool white dwarf stars as the Lyman α red wing formed by the collisions between atomic and molecular hydrogen and successfully explained entire spectra of many cool DA-type white dwarfs. Owing to the importa...

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Detalles Bibliográficos
Autores principales: Rohrmann, René, Althaus, Leandro Gabriel, Kepler, S. O.
Formato: Articulo
Lenguaje:Inglés
Publicado: 2011
Materias:
Ciencias Astronómicas
Atomic processes
Line: profiles
Molecular processes
Stars: atmospheres
White dwarfs
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/84021
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-84021
record_format dspace
institution Universidad Nacional de La Plata
institution_str I-19
repository_str R-120
collection SEDICI (UNLP)
language Inglés
topic Ciencias Astronómicas
Atomic processes
Line: profiles
Molecular processes
Stars: atmospheres
White dwarfs
spellingShingle Ciencias Astronómicas
Atomic processes
Line: profiles
Molecular processes
Stars: atmospheres
White dwarfs
Rohrmann, René
Althaus, Leandro Gabriel
Kepler, S. O.
Lyman α wing absorption in cool white dwarf stars
topic_facet Ciencias Astronómicas
Atomic processes
Line: profiles
Molecular processes
Stars: atmospheres
White dwarfs
description Kowalski & Saumon identified the missing absorption mechanism in the observed spectra of cool white dwarf stars as the Lyman α red wing formed by the collisions between atomic and molecular hydrogen and successfully explained entire spectra of many cool DA-type white dwarfs. Owing to the important astrophysical implications of this issue, we present here an independent assessment of the process. For this purpose, we compute free-free quasi-molecular absorption in Lyman α due to collisions with H and H<SUB>2</SUB> within the one-perturber, quasi-static approximation. Line cross-sections are obtained using theoretical molecular potentials to describe the interaction between the radiating atom and the perturber. The variation in the electric dipole transition moment with the interparticle distance is also considered. Six and two allowed electric dipole transitions due to H-H and H-H<SUB>2</SUB> collisions, respectively, are taken into account. The new theoretical Lyman α line profiles are then incorporated in our stellar atmosphere program for the computation of synthetic spectra and colours of DA-type white dwarfs. Illustrative model atmospheres and spectral energy distributions are computed, which show that Lyman α broadening by atoms and molecules has a significant effect on the white dwarf atmosphere models. The inclusion of this collision-induced opacity significantly reddens spectral energy distributions and affects the broad-band colour indices for model atmospheres with T<SUB>eff</SUB> < 5000K. These results confirm those previously obtained by Kowalski & Saumon. Our study points out the need for reliable evaluations of H<SUB>3</SUB> potential energy surfaces covering a large region of nuclear configurations, in order to obtain a better description of H-H<SUB>2</SUB> collisions and a more accurate evaluation of their influence on the spectrum of cool white dwarfs.
format Articulo
Articulo
author Rohrmann, René
Althaus, Leandro Gabriel
Kepler, S. O.
author_facet Rohrmann, René
Althaus, Leandro Gabriel
Kepler, S. O.
author_sort Rohrmann, René
title Lyman α wing absorption in cool white dwarf stars
title_short Lyman α wing absorption in cool white dwarf stars
title_full Lyman α wing absorption in cool white dwarf stars
title_fullStr Lyman α wing absorption in cool white dwarf stars
title_full_unstemmed Lyman α wing absorption in cool white dwarf stars
title_sort lyman α wing absorption in cool white dwarf stars
publishDate 2011
url http://sedici.unlp.edu.ar/handle/10915/84021
work_keys_str_mv AT rohrmannrene lymanawingabsorptionincoolwhitedwarfstars
AT althausleandrogabriel lymanawingabsorptionincoolwhitedwarfstars
AT keplerso lymanawingabsorptionincoolwhitedwarfstars
bdutipo_str Repositorios
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