Abstract
We discuss the Hubble Space Telescope Space Telescope Imaging Spectrograph UV echelle spectrum of the hot DA white dwarf REJ 1032+532. The interstellar data from this spectrum are presented by Holberg and coworkers. In this paper we discuss a number of strong photospheric features due to C, N, and Si that are present in the REJ 1032+532 spectrum. While the inferred heavy element content of REJ 1032+532 roughly matches the predictions of radiative levitation for carbon and silicon, the observed nitrogen abundance greatly exceeds predictions by a factor of 50. The observed shapes of the N v lines provide the first evidence, at UV wavelengths, of heavy element stratification in a hot DA white dwarf. Homogeneous models are unable to reproduce the shape of the REJ 1032+532 N v lines, nor can they account for the relatively low degree of EUV opacity in the star. We present a simple stratified nitrogen model that resolves these problems. The high degree of stratification in REJ 1032+532 is the signature of ongoing mass loss in this star. The radial velocity of REJ 1032+532 obtained with Space Telescope Imaging Spectrograph differs by 44 km s-1 from that obtained from the Balmer H I lines with the Multiple Mirror Telescope. This suggests that REJ 1032+532 is likely a member of a binary system containing either a late M star or another white dwarf.
Original language | English (US) |
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Pages (from-to) | 850-858 |
Number of pages | 9 |
Journal | Astrophysical Journal |
Volume | 517 |
Issue number | 2 PART 1 |
DOIs | |
State | Published - Jun 1 1999 |
Keywords
- Stars: abundances
- Ultraviolet: stars
- White dwarfs
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science