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A Search for Metal Lines in the Spectra of DA White DwarfsA theoretical analysis was carried out in order to interpret the ultraviolet spectra of DB white dwarfs obtained earlier with the International Ultraviolet Explorer (IUE) satellite. Here the results of the IUE ultraviolet spectroscopy combined with visual data and model atmospheres of DB white dwarfs are reported. In particular, a search for spectra lines due to the element carbon using the ultraviolet was made. In no case is there a positive detection of carbon and from these data, and upper limits for carbon by number relative to helium are derived in the range of C: He 10 to the minus 5 power to 10 to the minus 7 power for the 16 DB stars with ultraviolet spectra in the temperature range 11400 K T sub EFF less than 2300 K. The low carbon abundances found in the atmospheres of the DB stars agree well with the hypothesis that the atmospheric carbon observed in the cooler DQ members of the helium-rich white dwarf sequence is produced by a convective dredging mechanism.
Document ID
19860016791
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Wegner, G. A. (Dartmouth Coll. Hanover, NH, United States)
Date Acquired
September 5, 2013
Publication Date
June 5, 1986
Subject Category
Astronomy
Report/Patent Number
NAS 1.26:176825
NASA-CR-176825
Accession Number
86N26263
Funding Number(s)
CONTRACT_GRANT: NAG5-287
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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