HST/STIS spectroscopy of the exposed white dwarf in the short-period dwarf nova EK TrA

B. T. Gänsicke, P. Szkody, E. M. Sion, D. W. Hoard, S. Howell, F. H. Cheng, I. Hubeny

Research output: Contribution to journalArticle

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Abstract

We present high resolution Hubble Space Telescope ultraviolet spectroscopy of the dwarf nova EK TrA obtained in deep quiescence. The Space Telescope Imaging Spectrograph data reveal the broad Lyα absorption profile typical of a moderately cool white dwarf, overlayed by numerous broad emission lines of He, C, N, and Si and by a number of narrow absorption lines, mainly of C I and Si II. Assuming a white dwarf mass in the range 0.3-1.4 M we derive Teff = 17500-23400 K for the primary in EK TrA; Teff = 18800 K for a canonical mass of 0.6 M. From the narrow photospheric absorption lines, we measure the white dwarf rotational velocity, v sin i = 200 ± 100 km s-1. Even though the strong contamination of the photospheric white dwarf absorption spectrum by the emission lines prevents a detailed quantitative analysis of the chemical abundances of the atmosphere, the available data suggest slightly sub-solar abundances. The high time resolution of the STIS data allows us to associate the observed ultraviolet flickering with the emission lines, possibly originating in a hot optically thin corona above the cold accretion disk.

Original languageEnglish (US)
Pages (from-to)656-661
Number of pages6
JournalAstronomy and astrophysics
Volume374
Issue number2
DOIs
StatePublished - Jan 1 2001

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Keywords

  • Accretion, accretion disks
  • Stars: individual: EK TrA
  • Stars: novae, cataclysmic variables
  • Stars: white dwarfs
  • Ultraviolet: stars

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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