Reference : A seismic approach to testing different formation channels of subdwarf B stars
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/75389
A seismic approach to testing different formation channels of subdwarf B stars
English
Hu, Haili [Department of Astrophysics, IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL, Nijmegen, The Netherlands ; Institute of Astronomy, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium]
Dupret, Marc-Antoine [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique >]
Aerts, C. [Department of Astrophysics, IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL, Nijmegen, The Netherlands; Institute of Astronomy, Katholieke Universiteit Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium]
Nelemans, G. [Department of Astrophysics, IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL, Nijmegen, The Netherlands]
Kawaler, S. D. [Department of Physics and Astronomy, Iowa State Univeristy, Ames, IA 50014, USA]
Miglio, Andrea mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Evol. et stabilité des étoiles et des amas d'étoiles (ESEA) >]
Montalban Iglesias, Josefa mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie >]
Scuflaire, Richard [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Evol. et stabilité des étoiles et des amas d'étoiles (ESEA) >]
1-Oct-2008
Astronomy and Astrophysics
EDP Sciences
490
243-252
Yes (verified by ORBi)
International
0004-6361
1432-0746
Les Ulis
France
[en] stars: subdwarfs ; stars: evolution ; stars: oscillations ; methods: numerical
[en] Context: There are many unknowns in the formation of subdwarf B stars. Different formation channels are considered to be possible and to lead to a variety of helium-burning subdwarfs. All seismic models to date, however, assume that a subdwarf B star is a post-helium-flash-core surrounded by a thin inert layer of hydrogen. Aims: We examine an alternative formation channel, in which the subdwarf B star originates from a massive (>~2 M[SUB]o[/SUB]) red giant with a non-degenerate helium-core. Although these subdwarfs may evolve through the same region of the log g-T_eff diagram as the canonical post-flash subdwarfs, their interior structure is rather different. We examine how this difference affects their pulsation modes and whether it can be observed. Methods: Using detailed stellar evolution calculations we construct subdwarf B models from both formation channels. The iron accumulation in the driving region due to diffusion, which causes the excitation of the modes, is approximated by a Gaussian function. The pulsation modes and frequencies are calculated with a non-adiabatic pulsation code. Results: A detailed comparison of two subdwarf B models from different channels, but with the same log g and T_eff, shows that their mode excitation is different. The excited frequencies are lower for the post-flash than for the post-non-degenerate subdwarf B star. This is mainly due to the differing chemical composition of the stellar envelope. A more general comparison between two grids of models shows that the excited frequencies of most post-non-degenerate subdwarfs cannot be well-matched with the frequencies of post-flash subdwarfs. In the rare event that an acceptable seismic match is found, additional information, such as mode identification and log g and T_eff determinations, allows us to distinguish between the two formation channels.
http://hdl.handle.net/2268/75389
10.1051/0004-6361:200810233
http://adsabs.harvard.edu/abs/2008A%26A...490..243H
http://de.arxiv.org/abs/0808.3045

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