Astronomy and Astrophysics – Astrophysics
Scientific paper
2005-02-07
Astron.Astrophys. 435 (2005) 649-655
Astronomy and Astrophysics
Astrophysics
7 pages, 3 figures, 3 tables, accepted for publication in A&A
Scientific paper
10.1051/0004-6361:20042608
The helium-atmosphere (DB) white dwarfs are commonly thought to be the descendants of the hotter PG1159 stars, which initially have uniform He/C/O atmospheres. In this evolutionary scenario, diffusion builds a pure He surface layer which gradually thickens as the star cools. In the temperature range of the pulsating DB white dwarfs (T_eff ~ 25,000 K) this transformation is still taking place, allowing asteroseismic tests of the theory. We have obtained dual-site observations of the pulsating DB star CBS114, to complement existing observations of the slightly cooler star GD358. We recover the 7 independent pulsation modes that were previously known, and we discover 4 new ones to provide additional constraints on the models. We perform objective global fitting of our updated double-layered envelope models to both sets of observations, leading to determinations of the envelope masses and pure He surface layers that qualitatively agree with the expectations of diffusion theory. These results provide new asteroseismic evidence supporting one of the central assumptions of spectral evolution theory, linking the DB white dwarfs to PG1159 stars.
Edward Nather R.
Handler Gerald
Kim Seong-Lyun
Metcalfe Travis Scott
Park Byeong-Geon
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