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Heavy element abundances in DA white dwarfs

M. A. Barstow·M. R. Burleigh·N. P. Bannister·J. B. Holberg·I. Hubeny·F. C. Bruhweiler·R. Napiwotzki
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Abstract

We present a series of systematic abundance measurements for a group of hot DA white dwarfs in the temperature range 20,000-75,000K, based on far-UV spectroscopy with STIS on HST, IUE and FUSE. Using our latest heavy element blanketed non-LTE stellar atmosphere calculations we have addressed the heavy element abundance patterns for the hottest stars for the first time, showing that they are similar to objects like G191-B2B. The abundances observed in the cooler (<50,000K) white dwarfs are something of a mystery. Some of the patterns (e.g. REJ1032) can be explained by self-consistent levitation-diffusion calculations but there is then a serious difficulty in understanding the appearance of the apparently pure H atmospheres. We also report the detection of photospheric HeII in the atmosphere of WD2218+706.

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M. A. Barstow, M. R. Burleigh, N. P. Bannister, J. B. Holberg, I. Hubeny, F. C. Bruhweiler, R. Napiwotzki. 2000-10-23. Heavy element abundances in DA white dwarfs. https://arxiv.org/abs/astro-ph/0010448

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