Evidence of thin helium envelopes in PG 1159 stars

• Autores: Althaus, Leandro Gabriel; Córsico, Alejandro Hugo; Miller Bertolami, Marcelo Miguel; García-Berro, E.; Kepler, S. O.
• Año de publicación: 2008
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Ciencias Astronómicas; Dense matter; Diffusion; Stars: abundances; Stars: evolution; Stars: interiors; White dwarfs
• Institución: Universidad Nacional de La Plata

We present evidence that PG 1159 stars could harbor He-rich envelopes substantially thinner than those predicted by current evolutionary models with current estimates of mass loss, which may be attributable to an extensive mass-loss episode during the born-again AGB phase. Specifically, we show that the models with thin He-rich envelopes predict remarkably large magnitudes of the rates of period change of the trapped and untrapped modes observed in the pulsating star PG 1159-035. This is a consequence of the much shorter evolutionary timescale of the models with thin He-rich envelopes during the low-gravity PG 1159 regime. Our findings are particularly interesting in view of the suggestion of an evolutionary link between the helium-deficient PG 1159 star H1504+65 and the recently discovered white dwarfs with almost pure carbon atmospheres.
Facultad de Ciencias Astronómicas y Geofísicas