Astronomy and Astrophysics – Astrophysics
Scientific paper
Aug 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995a%26a...300l...5n&link_type=abstract
Astronomy and Astrophysics, v.300, p.L5
Astronomy and Astrophysics
Astrophysics
18
Stars: Individual: Hd 149499B, White Dwarfs, Stars: Fundamental Parameters, Ultraviolet: Stars, Ultraviolet: Ism
Scientific paper
We present an analysis of a hig-resolution FUV spectrum (912...1170Angstroems) of the cool DO white dwarf HD 149499 B. Observations were performed with the Berkeley EUV/FUV spectrometer of the ORFEUS experiment. The analysis, performed with a grid of LTE model atmospheres, yielded the basic parameters Teff = 49500+/-500K and log g = 7.97+/-0.08. The photospheric hydrogen Lyman lines in the FUV spectrum indicate the presence of hydrogen: log nH/nHe =-0.65+/-0.12.The implications of this finding for the spectral evolution of white dwarfs are discussed. A check of the LTE assumption was performed by a comparison with NLTE atmospheres calculated for appropriate parameters. The interstellar components of the hydrogen Lyman lines are used for an estimate of the hydrogen column towards the HD 149499 system: N_H_ about 1x10^19^/cm2.
Bowyer Stuart
Edelstein José
Hurwitz Margaret M.
Jordan Stefan
Koester Detlev
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