A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars

Autores
Schindewolf, M.; Németh, P.; Heber, U.; Battich, Tiara; Miller Bertolami, Marcelo Miguel; Irrgang, A.; Latour, M.
Año de publicación
2018
Idioma
inglés
Tipo de recurso
artículo
Estado
versión publicada
Descripción
Aims. Hot subdwarf stars represent a poorly understood late phase of stellar evolution. While binary evolution plays an important role for the formation of B-Type subdwarfs (sdB), the origin of the helium dominated subclass of O-Type subdwarfs (He-sdO) is still unknown. We search for chemical signatures of their genesis by means of quantitative spectral analyses of high-quality visual and ultraviolet spectra. Methods. Four prototypical He-sdO stars, one belonging to the nitrogen-rich and three to the C-rich subclass, were selected for which archival far-ultraviolet spectra from the FUSE satellite as well as high-resolution visual and UVA spectra taken with the ESO-UVES/FEROS spectrographs are available. Using Ta LUSTY200/Sa YNSPEC49 to compute line blanketed-non-local thermodynamic equilibrium (NLTE) model atmospheres and synthetic spectra, atmospheric parameters and the abundances patterns have been derived. The final models included H, He, C, N, O, Ne, Mg, Al, Si, P, S, Fe, and Ni represented by the most detailed model atoms available. Because of the enrichment of either nitrogen or carbon, it turned out, that models including these elements at the appropriate high abundance provide sufficiently accurate approximations to the temperature stratification of full models. Results. No indications for binarity were found, neither radial velocity variations nor photometric evidence for the presence of a companion could be detected. All stars have helium-dominated atmospheres almost free of hydrogen and temperatures between 42 000 K and 47 000 K while their surface gravities lie between log g = 5.4 and 5.7. The abundance pattern of CD-31°4800 displays the signatures of CNO burning, while heavier elements are subsolar by about 0.4 dex, except for Ne and Si which are close to solar. The abundance patterns of the C-rich He-sdOs are more complex. A slightly subsolar metallicity is accompanied by N-enrichment and O-deficiency, less pronounced than in CD-31°4800. Neon is mildly to strongly enriched, up to a factor of ten with respect to the sun in LS IV +10° 9. The nickel-To-iron ratio is significantly super-solar. Using spectral energy distributions and Gaia parallaxes the masses of the stars were determined. They are found to scatter around the canonical mass for the core helium flash, although the uncertainties are large. Conclusions. The abundance pattern observed for CD-31°4800 is consistent with predictions of models for slow (cold) mergers of pairs of equal mass helium WDs except for the low oxygen abundance observed. Models for composite mergers were considered for the C-rich stars, but predict abundance pattern dissimilar to those determined. [CW83] 0904-02, though, may be a candidate for a composite He-WD merger, as it rotates and appears to be more massive than the other program stars. New evolutionary models for the hot flasher scenario predict abundance patterns similar to those determined for the C-rich stars. Hence, C-rich He-sdO may well result from late He flashes with deep-mixing episodes.
Fil: Schindewolf, M.. Universitat Erlangen-Nuremberg; Alemania
Fil: Németh, P.. Universitat Erlangen-Nuremberg; Alemania
Fil: Heber, U.. Universitat Erlangen-Nuremberg; Alemania
Fil: Battich, Tiara. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina
Fil: Miller Bertolami, Marcelo Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina
Fil: Irrgang, A.. Universitat Erlangen-Nuremberg; Alemania
Fil: Latour, M.. Universitat Erlangen-Nuremberg; Alemania
Materia
STARS: ABUNDANCES
STARS: ATMOSPHERES
STARS: EVOLUTION
SUBDWARFS
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:11336/82514

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network_acronym_str CONICETDig
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network_name_str CONICET Digital (CONICET)
spelling A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O starsSchindewolf, M.Németh, P.Heber, U.Battich, TiaraMiller Bertolami, Marcelo MiguelIrrgang, A.Latour, M.STARS: ABUNDANCESSTARS: ATMOSPHERESSTARS: EVOLUTIONSUBDWARFShttps://purl.org/becyt/ford/1.3https://purl.org/becyt/ford/1Aims. Hot subdwarf stars represent a poorly understood late phase of stellar evolution. While binary evolution plays an important role for the formation of B-Type subdwarfs (sdB), the origin of the helium dominated subclass of O-Type subdwarfs (He-sdO) is still unknown. We search for chemical signatures of their genesis by means of quantitative spectral analyses of high-quality visual and ultraviolet spectra. Methods. Four prototypical He-sdO stars, one belonging to the nitrogen-rich and three to the C-rich subclass, were selected for which archival far-ultraviolet spectra from the FUSE satellite as well as high-resolution visual and UVA spectra taken with the ESO-UVES/FEROS spectrographs are available. Using Ta LUSTY200/Sa YNSPEC49 to compute line blanketed-non-local thermodynamic equilibrium (NLTE) model atmospheres and synthetic spectra, atmospheric parameters and the abundances patterns have been derived. The final models included H, He, C, N, O, Ne, Mg, Al, Si, P, S, Fe, and Ni represented by the most detailed model atoms available. Because of the enrichment of either nitrogen or carbon, it turned out, that models including these elements at the appropriate high abundance provide sufficiently accurate approximations to the temperature stratification of full models. Results. No indications for binarity were found, neither radial velocity variations nor photometric evidence for the presence of a companion could be detected. All stars have helium-dominated atmospheres almost free of hydrogen and temperatures between 42 000 K and 47 000 K while their surface gravities lie between log g = 5.4 and 5.7. The abundance pattern of CD-31°4800 displays the signatures of CNO burning, while heavier elements are subsolar by about 0.4 dex, except for Ne and Si which are close to solar. The abundance patterns of the C-rich He-sdOs are more complex. A slightly subsolar metallicity is accompanied by N-enrichment and O-deficiency, less pronounced than in CD-31°4800. Neon is mildly to strongly enriched, up to a factor of ten with respect to the sun in LS IV +10° 9. The nickel-To-iron ratio is significantly super-solar. Using spectral energy distributions and Gaia parallaxes the masses of the stars were determined. They are found to scatter around the canonical mass for the core helium flash, although the uncertainties are large. Conclusions. The abundance pattern observed for CD-31°4800 is consistent with predictions of models for slow (cold) mergers of pairs of equal mass helium WDs except for the low oxygen abundance observed. Models for composite mergers were considered for the C-rich stars, but predict abundance pattern dissimilar to those determined. [CW83] 0904-02, though, may be a candidate for a composite He-WD merger, as it rotates and appears to be more massive than the other program stars. New evolutionary models for the hot flasher scenario predict abundance patterns similar to those determined for the C-rich stars. Hence, C-rich He-sdO may well result from late He flashes with deep-mixing episodes.Fil: Schindewolf, M.. Universitat Erlangen-Nuremberg; AlemaniaFil: Németh, P.. Universitat Erlangen-Nuremberg; AlemaniaFil: Heber, U.. Universitat Erlangen-Nuremberg; AlemaniaFil: Battich, Tiara. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Miller Bertolami, Marcelo Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Irrgang, A.. Universitat Erlangen-Nuremberg; AlemaniaFil: Latour, M.. Universitat Erlangen-Nuremberg; AlemaniaEDP Sciences2018-12info: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/11336/82514Schindewolf, M.; Németh, P.; Heber, U.; Battich, Tiara; Miller Bertolami, Marcelo Miguel; et al.; A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars; EDP Sciences; Astronomy and Astrophysics; 620; A36; 12-2018; 1-320004-6361CONICET DigitalCONICETenginfo:eu-repo/semantics/altIdentifier/doi/10.1051/0004-6361/201732140info:eu-repo/semantics/altIdentifier/url/https://www.aanda.org/articles/aa/abs/2018/12/aa32140-17/aa32140-17.htmlinfo:eu-repo/semantics/openAccesshttps://creativecommons.org/licenses/by-nc-sa/2.5/ar/reponame:CONICET Digital (CONICET)instname:Consejo Nacional de Investigaciones Científicas y Técnicas2025-09-29T10:14:45Zoai:ri.conicet.gov.ar:11336/82514instacron: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 10:14:45.88CONICET Digital (CONICET) - Consejo Nacional de Investigaciones Científicas y Técnicasfalse
dc.title.none.fl_str_mv A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars
title A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars
spellingShingle A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars
Schindewolf, M.
STARS: ABUNDANCES
STARS: ATMOSPHERES
STARS: EVOLUTION
SUBDWARFS
title_short A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars
title_full A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars
title_fullStr A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars
title_full_unstemmed A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars
title_sort A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars
dc.creator.none.fl_str_mv Schindewolf, M.
Németh, P.
Heber, U.
Battich, Tiara
Miller Bertolami, Marcelo Miguel
Irrgang, A.
Latour, M.
author Schindewolf, M.
author_facet Schindewolf, M.
Németh, P.
Heber, U.
Battich, Tiara
Miller Bertolami, Marcelo Miguel
Irrgang, A.
Latour, M.
author_role author
author2 Németh, P.
Heber, U.
Battich, Tiara
Miller Bertolami, Marcelo Miguel
Irrgang, A.
Latour, M.
author2_role author
author
author
author
author
author
dc.subject.none.fl_str_mv STARS: ABUNDANCES
STARS: ATMOSPHERES
STARS: EVOLUTION
SUBDWARFS
topic STARS: ABUNDANCES
STARS: ATMOSPHERES
STARS: EVOLUTION
SUBDWARFS
purl_subject.fl_str_mv https://purl.org/becyt/ford/1.3
https://purl.org/becyt/ford/1
dc.description.none.fl_txt_mv Aims. Hot subdwarf stars represent a poorly understood late phase of stellar evolution. While binary evolution plays an important role for the formation of B-Type subdwarfs (sdB), the origin of the helium dominated subclass of O-Type subdwarfs (He-sdO) is still unknown. We search for chemical signatures of their genesis by means of quantitative spectral analyses of high-quality visual and ultraviolet spectra. Methods. Four prototypical He-sdO stars, one belonging to the nitrogen-rich and three to the C-rich subclass, were selected for which archival far-ultraviolet spectra from the FUSE satellite as well as high-resolution visual and UVA spectra taken with the ESO-UVES/FEROS spectrographs are available. Using Ta LUSTY200/Sa YNSPEC49 to compute line blanketed-non-local thermodynamic equilibrium (NLTE) model atmospheres and synthetic spectra, atmospheric parameters and the abundances patterns have been derived. The final models included H, He, C, N, O, Ne, Mg, Al, Si, P, S, Fe, and Ni represented by the most detailed model atoms available. Because of the enrichment of either nitrogen or carbon, it turned out, that models including these elements at the appropriate high abundance provide sufficiently accurate approximations to the temperature stratification of full models. Results. No indications for binarity were found, neither radial velocity variations nor photometric evidence for the presence of a companion could be detected. All stars have helium-dominated atmospheres almost free of hydrogen and temperatures between 42 000 K and 47 000 K while their surface gravities lie between log g = 5.4 and 5.7. The abundance pattern of CD-31°4800 displays the signatures of CNO burning, while heavier elements are subsolar by about 0.4 dex, except for Ne and Si which are close to solar. The abundance patterns of the C-rich He-sdOs are more complex. A slightly subsolar metallicity is accompanied by N-enrichment and O-deficiency, less pronounced than in CD-31°4800. Neon is mildly to strongly enriched, up to a factor of ten with respect to the sun in LS IV +10° 9. The nickel-To-iron ratio is significantly super-solar. Using spectral energy distributions and Gaia parallaxes the masses of the stars were determined. They are found to scatter around the canonical mass for the core helium flash, although the uncertainties are large. Conclusions. The abundance pattern observed for CD-31°4800 is consistent with predictions of models for slow (cold) mergers of pairs of equal mass helium WDs except for the low oxygen abundance observed. Models for composite mergers were considered for the C-rich stars, but predict abundance pattern dissimilar to those determined. [CW83] 0904-02, though, may be a candidate for a composite He-WD merger, as it rotates and appears to be more massive than the other program stars. New evolutionary models for the hot flasher scenario predict abundance patterns similar to those determined for the C-rich stars. Hence, C-rich He-sdO may well result from late He flashes with deep-mixing episodes.
Fil: Schindewolf, M.. Universitat Erlangen-Nuremberg; Alemania
Fil: Németh, P.. Universitat Erlangen-Nuremberg; Alemania
Fil: Heber, U.. Universitat Erlangen-Nuremberg; Alemania
Fil: Battich, Tiara. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina
Fil: Miller Bertolami, Marcelo Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; Argentina
Fil: Irrgang, A.. Universitat Erlangen-Nuremberg; Alemania
Fil: Latour, M.. Universitat Erlangen-Nuremberg; Alemania
description Aims. Hot subdwarf stars represent a poorly understood late phase of stellar evolution. While binary evolution plays an important role for the formation of B-Type subdwarfs (sdB), the origin of the helium dominated subclass of O-Type subdwarfs (He-sdO) is still unknown. We search for chemical signatures of their genesis by means of quantitative spectral analyses of high-quality visual and ultraviolet spectra. Methods. Four prototypical He-sdO stars, one belonging to the nitrogen-rich and three to the C-rich subclass, were selected for which archival far-ultraviolet spectra from the FUSE satellite as well as high-resolution visual and UVA spectra taken with the ESO-UVES/FEROS spectrographs are available. Using Ta LUSTY200/Sa YNSPEC49 to compute line blanketed-non-local thermodynamic equilibrium (NLTE) model atmospheres and synthetic spectra, atmospheric parameters and the abundances patterns have been derived. The final models included H, He, C, N, O, Ne, Mg, Al, Si, P, S, Fe, and Ni represented by the most detailed model atoms available. Because of the enrichment of either nitrogen or carbon, it turned out, that models including these elements at the appropriate high abundance provide sufficiently accurate approximations to the temperature stratification of full models. Results. No indications for binarity were found, neither radial velocity variations nor photometric evidence for the presence of a companion could be detected. All stars have helium-dominated atmospheres almost free of hydrogen and temperatures between 42 000 K and 47 000 K while their surface gravities lie between log g = 5.4 and 5.7. The abundance pattern of CD-31°4800 displays the signatures of CNO burning, while heavier elements are subsolar by about 0.4 dex, except for Ne and Si which are close to solar. The abundance patterns of the C-rich He-sdOs are more complex. A slightly subsolar metallicity is accompanied by N-enrichment and O-deficiency, less pronounced than in CD-31°4800. Neon is mildly to strongly enriched, up to a factor of ten with respect to the sun in LS IV +10° 9. The nickel-To-iron ratio is significantly super-solar. Using spectral energy distributions and Gaia parallaxes the masses of the stars were determined. They are found to scatter around the canonical mass for the core helium flash, although the uncertainties are large. Conclusions. The abundance pattern observed for CD-31°4800 is consistent with predictions of models for slow (cold) mergers of pairs of equal mass helium WDs except for the low oxygen abundance observed. Models for composite mergers were considered for the C-rich stars, but predict abundance pattern dissimilar to those determined. [CW83] 0904-02, though, may be a candidate for a composite He-WD merger, as it rotates and appears to be more massive than the other program stars. New evolutionary models for the hot flasher scenario predict abundance patterns similar to those determined for the C-rich stars. Hence, C-rich He-sdO may well result from late He flashes with deep-mixing episodes.
publishDate 2018
dc.date.none.fl_str_mv 2018-12
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/11336/82514
Schindewolf, M.; Németh, P.; Heber, U.; Battich, Tiara; Miller Bertolami, Marcelo Miguel; et al.; A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars; EDP Sciences; Astronomy and Astrophysics; 620; A36; 12-2018; 1-32
0004-6361
CONICET Digital
CONICET
url http://hdl.handle.net/11336/82514
identifier_str_mv Schindewolf, M.; Németh, P.; Heber, U.; Battich, Tiara; Miller Bertolami, Marcelo Miguel; et al.; A quantitative NLTE analysis of visual and ultraviolet spectra of four helium-rich subdwarf O stars; EDP Sciences; Astronomy and Astrophysics; 620; A36; 12-2018; 1-32
0004-6361
CONICET Digital
CONICET
dc.language.none.fl_str_mv eng
language eng
dc.relation.none.fl_str_mv info:eu-repo/semantics/altIdentifier/doi/10.1051/0004-6361/201732140
info:eu-repo/semantics/altIdentifier/url/https://www.aanda.org/articles/aa/abs/2018/12/aa32140-17/aa32140-17.html
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
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dc.publisher.none.fl_str_mv EDP Sciences
publisher.none.fl_str_mv EDP Sciences
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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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