Journal Article

Asteroseismic constraints on diffusion in white dwarf envelopes

A. Bischoff-Kim and T. S. Metcalfe

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 1, pages 404-409
Published in print June 2011 | ISSN: 0035-8711
Published online June 2011 | e-ISSN: 1365-2966 | DOI: https://dx.doi.org/10.1111/j.1365-2966.2011.18396.x
Asteroseismic constraints on diffusion in white dwarf envelopes

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The asteroseismic analysis of white dwarfs allows us to peer below their photospheres and determine their internal structure. At ∼28 000 K EC20058−5234 is the hottest known pulsating helium atmosphere white dwarf. As such, it constitutes an important link in the evolution of white dwarfs down the cooling track. It is also astrophysically interesting because it is at a temperature where white dwarfs are expected to cool mainly through the emission of plasmon neutrinos. In the present work, we perform an asteroseismic analysis of EC20058−5234 and place the results in the context of stellar evolution and time-dependent diffusion calculations. We use a parallel genetic algorithm complemented with targeted grid searches to find the models that fit the observed periods best. Comparing our results with similar modelling of EC20058−5234’s cooler cousin CBS114, we find a helium envelope thickness consistent with time-dependent diffusion calculations and obtain a precise mode identification for EC20058−5234.

Keywords: diffusion; stars: evolution; stars: interiors; stars: oscillations; white dwarfs

Journal Article.  4353 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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