Lyman-alpha wing absorption in cool white dwarf stars

Autores
Rohrmann, Rene Daniel; Althaus, Leandro Gabriel; Kepler, S. O.
Año de publicación
2011
Idioma
inglés
Tipo de recurso
artículo
Estado
versión publicada
Descripción
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 H2 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–H2 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 Teff < 5000 K. These results confirm those previously obtained by Kowalski & Saumon. Our study points out the need for reliable evaluations of H3 potential energy surfaces covering a large region of nuclear configurations, in order to obtain a better description of H–H2 collisions and a more accurate evaluation of their influence on the spectrum of cool white dwarfs.
Fil: Rohrmann, Rene Daniel. Consejo Nacional de Investigaciones Cienti­ficas y Tecnicas. Centro Cientifico Tecnologico San Juan. Instituto de Ciencias Astronomicas de la Tierra y del Espacio; Argentina
Fil: Althaus, Leandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Astrofísica de La Plata; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina
Fil: Kepler, S. O.. Universidade Federal do Rio Grande do Sul; Brasil
Materia
Absortion lines
Atmospheres of stars
Atomic processes
Molecular processes
White dwarfs
Nivel de accesibilidad
acceso abierto
Condiciones de uso
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
Repositorio
CONICET Digital (CONICET)
Institución
Consejo Nacional de Investigaciones Científicas y Técnicas
OAI Identificador
oai:ri.conicet.gov.ar:11336/9712

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repository_id_str 3498
network_name_str CONICET Digital (CONICET)
spelling Lyman-alpha wing absorption in cool white dwarf starsRohrmann, Rene DanielAlthaus, Leandro GabrielKepler, S. O.Absortion linesAtmospheres of starsAtomic processesMolecular processesWhite dwarfshttps://purl.org/becyt/ford/1.3https://purl.org/becyt/ford/1Kowalski & 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 H2 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–H2 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 Teff < 5000 K. These results confirm those previously obtained by Kowalski & Saumon. Our study points out the need for reliable evaluations of H3 potential energy surfaces covering a large region of nuclear configurations, in order to obtain a better description of H–H2 collisions and a more accurate evaluation of their influence on the spectrum of cool white dwarfs.Fil: Rohrmann, Rene Daniel. Consejo Nacional de Investigaciones Cienti­ficas y Tecnicas. Centro Cientifico Tecnologico San Juan. Instituto de Ciencias Astronomicas de la Tierra y del Espacio; ArgentinaFil: Althaus, Leandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Astrofísica de La Plata; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Kepler, S. O.. Universidade Federal do Rio Grande do Sul; BrasilWiley2011-02info:eu-repo/semantics/articleinfo:eu-repo/semantics/publishedVersionhttp://purl.org/coar/resource_type/c_6501info:ar-repo/semantics/articuloapplication/pdfapplication/pdfapplication/pdfhttp://hdl.handle.net/11336/9712Rohrmann, Rene Daniel; Althaus, Leandro Gabriel; Kepler, S. O.; Lyman-alpha wing absorption in cool white dwarf stars; Wiley; Monthly Notices Of The Royal Astronomical Society; 411; 2-2011; 781-7910035-8711enginfo:eu-repo/semantics/altIdentifier/arxiv/http://dx.doi.org/10.1111/j.1365-2966.2010.17716.xinfo:eu-repo/semantics/altIdentifier/url/http://mnras.oxfordjournals.org/content/411/2/781info:eu-repo/semantics/openAccesshttps://creativecommons.org/licenses/by-nc-sa/2.5/ar/reponame:CONICET Digital (CONICET)instname:Consejo Nacional de Investigaciones Científicas y Técnicas2025-09-29T09:34:31Zoai:ri.conicet.gov.ar:11336/9712instacron:CONICETInstitucionalhttp://ri.conicet.gov.ar/Organismo científico-tecnológicoNo correspondehttp://ri.conicet.gov.ar/oai/requestdasensio@conicet.gov.ar; lcarlino@conicet.gov.arArgentinaNo correspondeNo correspondeNo correspondeopendoar:34982025-09-29 09:34:32.045CONICET Digital (CONICET) - Consejo Nacional de Investigaciones Científicas y Técnicasfalse
dc.title.none.fl_str_mv Lyman-alpha wing absorption in cool white dwarf stars
title Lyman-alpha wing absorption in cool white dwarf stars
spellingShingle Lyman-alpha wing absorption in cool white dwarf stars
Rohrmann, Rene Daniel
Absortion lines
Atmospheres of stars
Atomic processes
Molecular processes
White dwarfs
title_short Lyman-alpha wing absorption in cool white dwarf stars
title_full Lyman-alpha wing absorption in cool white dwarf stars
title_fullStr Lyman-alpha wing absorption in cool white dwarf stars
title_full_unstemmed Lyman-alpha wing absorption in cool white dwarf stars
title_sort Lyman-alpha wing absorption in cool white dwarf stars
dc.creator.none.fl_str_mv Rohrmann, Rene Daniel
Althaus, Leandro Gabriel
Kepler, S. O.
author Rohrmann, Rene Daniel
author_facet Rohrmann, Rene Daniel
Althaus, Leandro Gabriel
Kepler, S. O.
author_role author
author2 Althaus, Leandro Gabriel
Kepler, S. O.
author2_role author
author
dc.subject.none.fl_str_mv Absortion lines
Atmospheres of stars
Atomic processes
Molecular processes
White dwarfs
topic Absortion lines
Atmospheres of stars
Atomic processes
Molecular processes
White dwarfs
purl_subject.fl_str_mv https://purl.org/becyt/ford/1.3
https://purl.org/becyt/ford/1
dc.description.none.fl_txt_mv 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 H2 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–H2 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 Teff < 5000 K. These results confirm those previously obtained by Kowalski & Saumon. Our study points out the need for reliable evaluations of H3 potential energy surfaces covering a large region of nuclear configurations, in order to obtain a better description of H–H2 collisions and a more accurate evaluation of their influence on the spectrum of cool white dwarfs.
Fil: Rohrmann, Rene Daniel. Consejo Nacional de Investigaciones Cienti­ficas y Tecnicas. Centro Cientifico Tecnologico San Juan. Instituto de Ciencias Astronomicas de la Tierra y del Espacio; Argentina
Fil: Althaus, Leandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico La Plata. Instituto de Astrofísica de La Plata; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentina
Fil: Kepler, S. O.. Universidade Federal do Rio Grande do Sul; Brasil
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 H2 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–H2 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 Teff < 5000 K. These results confirm those previously obtained by Kowalski & Saumon. Our study points out the need for reliable evaluations of H3 potential energy surfaces covering a large region of nuclear configurations, in order to obtain a better description of H–H2 collisions and a more accurate evaluation of their influence on the spectrum of cool white dwarfs.
publishDate 2011
dc.date.none.fl_str_mv 2011-02
dc.type.none.fl_str_mv info:eu-repo/semantics/article
info:eu-repo/semantics/publishedVersion
http://purl.org/coar/resource_type/c_6501
info:ar-repo/semantics/articulo
format article
status_str publishedVersion
dc.identifier.none.fl_str_mv http://hdl.handle.net/11336/9712
Rohrmann, Rene Daniel; Althaus, Leandro Gabriel; Kepler, S. O.; Lyman-alpha wing absorption in cool white dwarf stars; Wiley; Monthly Notices Of The Royal Astronomical Society; 411; 2-2011; 781-791
0035-8711
url http://hdl.handle.net/11336/9712
identifier_str_mv Rohrmann, Rene Daniel; Althaus, Leandro Gabriel; Kepler, S. O.; Lyman-alpha wing absorption in cool white dwarf stars; Wiley; Monthly Notices Of The Royal Astronomical Society; 411; 2-2011; 781-791
0035-8711
dc.language.none.fl_str_mv eng
language eng
dc.relation.none.fl_str_mv info:eu-repo/semantics/altIdentifier/arxiv/http://dx.doi.org/10.1111/j.1365-2966.2010.17716.x
info:eu-repo/semantics/altIdentifier/url/http://mnras.oxfordjournals.org/content/411/2/781
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
eu_rights_str_mv openAccess
rights_invalid_str_mv https://creativecommons.org/licenses/by-nc-sa/2.5/ar/
dc.format.none.fl_str_mv application/pdf
application/pdf
application/pdf
dc.publisher.none.fl_str_mv Wiley
publisher.none.fl_str_mv Wiley
dc.source.none.fl_str_mv reponame:CONICET Digital (CONICET)
instname:Consejo Nacional de Investigaciones Científicas y Técnicas
reponame_str CONICET Digital (CONICET)
collection CONICET Digital (CONICET)
instname_str Consejo Nacional de Investigaciones Científicas y Técnicas
repository.name.fl_str_mv CONICET Digital (CONICET) - Consejo Nacional de Investigaciones Científicas y Técnicas
repository.mail.fl_str_mv dasensio@conicet.gov.ar; lcarlino@conicet.gov.ar
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