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Discovery of a white dwarf companion (MS0354.6-3650 = EUVE J0356-366) to a G2V star
We present x-ray, ultraviolet, and optical observations of the mysterious EUV/soft x-ray source EUVE J0356-336 (= MS0354.6-3650). Initial Einstein observations identified this source with a cluster of galaxies, but the relatively high source count rate in the Extreme Ultraviolet Explorer (EUVE) 100 A band and the lack of variability hinted that EUVE J0356-3650 might be a white dwarf; the UK Schmidt plate of the field surrounding this object found a 12.45 magnitude G2V star that could hide a compact companion. This hypothesis was confirmed in an IUE ultraviolet spectrum that shows the definite signature of a hydrogen-rich white dwarf (DA). A model atmosphere analysis shows that the DA star is hot (Teff?52,000 K) and may have a low abundance of heavy elements. We show that the G2V star and the DA star form a physical pair at a distance of 400 pc and therefore add to the list of white dwarf plus luminous main sequence star binaries discovered in EUV surveys.