Observations of Circumstellar Gas Associated With Hot White Dwarfs

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Session 46 -- White Dwarfs
Display presentation, Tuesday, 10, 1995, 9:20am - 6:30pm

[46.03] Observations of Circumstellar Gas Associated With Hot White Dwarfs

J.B. Holberg, J. Collins (U. Arizona/LPL), R.W. Tweedy (U. Arizona/Steward), F.C. Bruhweiler (Catholic U.), E.M. Sion (Villanova), M.A. Barstow (Leicester)

Recent IUE echelle observations of hot white dwarfs provide new information concerning of the nature of circumstellar gas seen in association with several of these stars. While prior IUE observations have clearly indicated the existence of such gas, due primarily to ions of Si and C, little is known regarding its location, physical state, or origin. We present coadded IUE echelle spectra of several white dwarfs in which new aspects of the narrow interstellar-like lines are seen. For one of these stars, CD -38\deg\ 10980, detailed observations indicate that the circumstellar gas resides deep within the gravitational potential well of the white dwarf and is subject to significant photoexcitation. We present first-time determinations of column densities for the ions involved and constraints on the electron densities in the gas in which the circumstellar lines originate. This work supported by NASA Grant NAGW5-2738.

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