ULTRAVIOLET SPECTROSCOPY OF THE DBV-WHITE-DWARF STAR-GD-358

We report on analysis of UV spectra of the DBV GD 358 obtained with th e Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope (HST). We confirm the detection of He II (1640 Angstrom and C II (1335 Angstrom reported by Sion et al. in 1988. The He II feature indicates a temperature of 27,000 +/- 1000 K, somewhat higher than pr evious estimates. We derive a carbon abundance -5.75 < log [n(C)/n(He) ] < -5.55. In addition, we detect, for the first time, hydrogen in the spectrum. Whether this hydrogen is either photospheric or interstella r, the inferred photospheric upper limit is log [n(H)/n(He)] < -5, tra nslating into a mass of <5 x 10(-18)M. We discuss the implications of these findings on GD 358's asteroseismologically determined structure and the impact on theories of white dwarf formation and evolution.