Journal Article

The distribution of metals in hot DA white dwarfs

N. J. Dickinson, M. A. Barstow and I. Hubeny

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 421, issue 4, pages 3222-3228
Published in print April 2012 | ISSN: 0035-8711
Published online April 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.20545.x
The distribution of metals in hot DA white dwarfs

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The importance to stellar evolution of understanding the metal abundances in hot white dwarfs is well known. Previous work has found the hot DA white dwarfs REJ 1032+532, REJ 1614−085 and GD 659 to have highly abundant, stratified photospheric nitrogen, due to the narrow absorption‐line profiles of the far‐ultraviolet (FUV) N v doublet and the lack of extreme‐ultraviolet (EUV) continuum absorption. A preliminary analysis of the extremely narrow, deep line profiles of the photospheric metal absorption features of PG 0948+534 suggested a similar photospheric metal configuration. However, other studies have found that REJ 1032+532, REJ 1614−085 and GD 659 can be well described by homogeneous models, with nitrogen abundances more in keeping with those of white dwarfs with higher effective temperatures. Here, a re‐analysis of the nitrogen absorption features seen in REJ 1032+532, REJ 1614−085 and GD 659 is presented, with the aim of better understanding the structure of these stars, to test which models better represent the observed data and apply the results to the line profiles seen in PG 0948+534. A degeneracy is seen in the modelling of the nitrogen absorption‐line profiles of REJ 1032+532, REJ 1614−085 and GD 659, with low‐abundance, homogeneously distributed nitrogen models most likely being a better representation of the observed data. In PG 0948+534, no such degeneracy is seen, and the enigmatically deep line profiles could not be modelled satisfactorily.

Keywords: stars: abundances; stars: atmospheres; white dwarfs; ultraviolet: stars

Journal Article.  4124 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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