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The close DAO+dM binary RE J0720-318: a stratified white dwarf with a thin H layer and a possible circumbinary disk

journal contribution
posted on 2023-05-17, 14:44 authored by Burleigh, MR, Barstow, MA, Dobbie, PD
We have analysed the EUVE spectrum of the DAO white dwarf RE J0720-318. In contrast to the optical spectrum, which can only be fitted with a homogeneously mixed H+He atmosphere, we find the EUVE spectrum can only be matched with a stratified structure. The H layer mass of 3x10-14 M⊙, is a factor of ~10 below upper limits from previous EUVE observations of white dwarfs. In addition, we detect an unprecedented HeI/HI ratio of ~1 for the absorbing column along the line of sight, implying an H ionization fraction >90% if all this material resides in the local ISM. We suggest that, since this is a close pre-CV binary system, most of the helium probably lies within the immediate vicinity of the star, possibly in the form of a circumbinary disk left over from the common envelope (CE) phase. These results have important implications for our understanding of the evolutionary status of DAO white dwarfs in particular, and for post-CE binaries in general.

History

Publication title

Astronomy & Astrophysics

Volume

317

Pagination

L27-L30

ISSN

0004-6361

Department/School

School of Natural Sciences

Publisher

EDP Sciences

Place of publication

Les Ulis Cedex A France

Rights statement

Copyright 1997 Astronomy and Astrophysics

Repository Status

  • Restricted

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Expanding knowledge in the physical sciences

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