An asteroseismic test of diffusion theory in white dwarfs

Author(s): Travis S. Metcalfe, R. Edward Nather, Todd K. Watson, S -L Kim, Byeong G Park, Gerald Handler
Abstract: The helium-atmosphere (DB) white dwarfs are commonly thought to be the descendants of the hotter PG 1159 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 (Teff ~ 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 CBS 114, to complement existing observations of the slightly cooler star GD 358. 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 PG 1159 stars. Œ ESO 2005.
Organisation(s): Department of Astrophysics
External organisation(s): University of Texas, Austin, Southwestern University, Korea Astronomy and Space Science Institute
Journal: Astronomy & Astrophysics
Volume: 435
Pages: 649-655
No. of pages: 7
ISSN: 0004-6361
DOI: https://doi.org/10.1051/0004-6361:20042608
Publication date: 2005
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy
Portal url: https://ucrisportal.univie.ac.at/en/publications/b37bcd16-538b-4562-bf2b-6dd98a6feb6b

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