Far-ultraviolet space telescope imaging spectrograph spectra of the white dwarf REJ 1032+532. II. Stellar spectrum

J. B. Holberg, M. A. Barstow, F. C. Bruhweiler, I. Hubeny, E. M. Green

Research output: Contribution to journalArticle

13 Scopus citations

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 languageEnglish (US)
Pages (from-to)850-858
Number of pages9
JournalAstrophysical Journal
Volume517
Issue number2 PART 1
DOIs
StatePublished - Jun 1 1999

Keywords

  • Stars: abundances
  • Ultraviolet: stars
  • White dwarfs

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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