Low-mass, helium-enriched PG1159 stars: A possible evolutionary origin and implications for their pulsational stability properties

Aims, We examine a recently-proposed evolutionary scenario that could explain the existence of the low-mass, helium-enriched PG 1159 stars. We focus in particular on studying the pulsational stability properties of the evolutionary models predicted by such a scenario. Methods. We assess the overst...

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Detalles Bibliográficos
Autores principales: Althaus, Leandro Gabriel, Córsico, Alejandro Hugo, Miller Bertolami, Marcelo Miguel
Formato: Articulo
Lenguaje:Inglés
Publicado: 2007
Materias:
Ciencias Astronómicas
Stars: abundances
Stars: AGB and post-AGB
Stars: evolution
Stars: interiors
Stars: variables: general
White dwarfs
Acceso en línea:http://sedici.unlp.edu.ar/handle/10915/83336
Aporte de:
SEDICI (UNLP) de Universidad Nacional de La Plata
id I19-R120-10915-83336
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
Stars: abundances
Stars: AGB and post-AGB
Stars: evolution
Stars: interiors
Stars: variables: general
White dwarfs
spellingShingle Ciencias Astronómicas
Stars: abundances
Stars: AGB and post-AGB
Stars: evolution
Stars: interiors
Stars: variables: general
White dwarfs
Althaus, Leandro Gabriel
Córsico, Alejandro Hugo
Miller Bertolami, Marcelo Miguel
Low-mass, helium-enriched PG1159 stars: A possible evolutionary origin and implications for their pulsational stability properties
topic_facet Ciencias Astronómicas
Stars: abundances
Stars: AGB and post-AGB
Stars: evolution
Stars: interiors
Stars: variables: general
White dwarfs
description Aims, We examine a recently-proposed evolutionary scenario that could explain the existence of the low-mass, helium-enriched PG 1159 stars. We focus in particular on studying the pulsational stability properties of the evolutionary models predicted by such a scenario. Methods. We assess the overstability of pulsation g-modes of stellar models as evolution proceeds in the PG 1159 domain. Stellar models are extracted from the full evolution of a 1-M⊙ model star that experiences its first thermal pulse as a late thermal pulse (LTP) after leaving the AGB. The evolutionary stages corresponding to the born-again episode and the subsequent helium sub-flashes are taken into account in detail. Results. Under reasonable assumptions of mass-loss rate, the evolutionary scenario reproduces the high helium abundances observed in some PG 1159 stars. We find that, despite the high helium abundance in the driving layers, a narrow region exists in the log T<SUB>eff</SUB> - log g diagram for which the helium-enriched PG 1159 sequence exhibits unstable pulsation modes with periods in the range 500 to 1600 s. In particular, the nonpulsating helium-enriched PG 1159 star, MCT 0130-1937, is located outside the theoretical instability domain. Our results suggest that MCT 0130-1937 is a real non-pulsating star and that the lack of pulsations should not be attributed to unfavorable geometry. Conclusions. Our study hints at a consistent picture between the evolutionary scenario that could explain the existence of heliumenriched PG 1159 stars and the nonvariable nature of MCT 0130-1937. We also present theoretical support for the unusually high helium abundance observed in the nonpulsating PG 1159 star HS 1517+7403. We suggest that HS 1517+7403 could be a transition object linking the low-mass helium-rich O(He) stars with the helium-enriched PG 1159 stars via the evolutionary connection K1-27 →HS 1517+7403 → MCT 0130-1937.
format Articulo
Articulo
author Althaus, Leandro Gabriel
Córsico, Alejandro Hugo
Miller Bertolami, Marcelo Miguel
author_facet Althaus, Leandro Gabriel
Córsico, Alejandro Hugo
Miller Bertolami, Marcelo Miguel
author_sort Althaus, Leandro Gabriel
title Low-mass, helium-enriched PG1159 stars: A possible evolutionary origin and implications for their pulsational stability properties
title_short Low-mass, helium-enriched PG1159 stars: A possible evolutionary origin and implications for their pulsational stability properties
title_full Low-mass, helium-enriched PG1159 stars: A possible evolutionary origin and implications for their pulsational stability properties
title_fullStr Low-mass, helium-enriched PG1159 stars: A possible evolutionary origin and implications for their pulsational stability properties
title_full_unstemmed Low-mass, helium-enriched PG1159 stars: A possible evolutionary origin and implications for their pulsational stability properties
title_sort low-mass, helium-enriched pg1159 stars: a possible evolutionary origin and implications for their pulsational stability properties
publishDate 2007
url http://sedici.unlp.edu.ar/handle/10915/83336
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AT corsicoalejandrohugo lowmassheliumenrichedpg1159starsapossibleevolutionaryoriginandimplicationsfortheirpulsationalstabilityproperties
AT millerbertolamimarcelomiguel lowmassheliumenrichedpg1159starsapossibleevolutionaryoriginandimplicationsfortheirpulsationalstabilityproperties
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