Far-ultraviolet spectroscopy of the hot DA white dwarf WD 2218+706 (DeHt5) with STIS

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

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

We report a study of the photospheric composition of the hot DA white dwarf WD 2218 + 706, which is also the central star of the old planetary nebula DeHt5. Helium is detected in the farUV spectrum. In addition, the star clearly contains significant quantities of elements heavier than He at abundances generally a factor of 2 to 10 higher than those found in the archetypal heavy element-rich DA G191-B2B. This is the first detection of trace He using the He II λ1640 line in an isolated DA white dwarf, but the low surface gravity is more indicative of a binary evolution route from the red giant branch rather than a path along the asymptotic giant branch (AGB) as a single star. However, the absence of any evidence for a companion star and the uncertainty in the measured mass for WD 2218 + 706 still allow the possibility of an origin along an AGB evolutionary track. We reanalyse the existing optical spectra of WD 2218 + 706 using our latest pure H and heavy element-rich model atmospheres, obtaining a good match between the observed and synthetic spectra with either set of models. We find little evidence of any inconsistency in the temperature required to fit individual Balmer lines, as reported elsewhere for this star. Any discrepancies we see are confined to the Hα line and the core of Hβ but they do not compromise our analysis.

Original languageEnglish (US)
Pages (from-to)1149-1156
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Volume325
Issue number3
DOIs
StatePublished - Aug 11 2001

Keywords

  • Planetary nebulae: individual: DeHt5
  • Stars - atmospheres
  • Stars: abundances
  • Stars: individual: WD 2218 + 706
  • Ultraviolet: stars
  • White dwarfs

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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