Astronomy and Astrophysics – Astronomy
Scientific paper
Aug 2001
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001pasp..113..937s&link_type=abstract
The Publications of the Astronomical Society of the Pacific, Volume 113, Issue 786, pp. 937-943.
Astronomy and Astrophysics
Astronomy
Quasars: Individual (Uitboc 1574, J0943-1403), Stars: Individual (J094545-1417), Stars: Subdwarfs, Stars: White Dwarfs
Scientific paper
We have obtained the optical spectrum (3750-7500 Å) and ultraviolet fluxes at 1521 and 2260 Å for the quasar candidate UITBOC 1574. The optical spectrum shows strong Balmer absorption lines through at least n=9 and the He II line at 4686 Å. We compared the optical spectrum with non-LTE stellar atmosphere models and find Teff=46,900+/-3,000 K, logg=5.6+/-0.3, and helium abundance log(He/H)=-2.0+/-0.4. We classify the object as a hot subdwarf O star (sdO). With its high effective temperature and low helium abundance, UITBOC 1574 may be considered as belonging to the hot end of the subdwarf B population. The location of this object on the theoretical Teff-g diagram suggests that it is most likely in a post-extreme horizontal branch evolutionary stage. However, we cannot exclude the possibility that UITBOC 1574 may be a low-mass helium white dwarf precursor. We estimate a spectroscopic distance of 5.6+/-1.7 kpc with a height of 2.7 +/- 0.8 kpc above the Galactic plane if it is a helium-poor sdO. The heliocentric radial velocity of the star is 89 +/- 18 km s-1. Based on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium.
Chayer Pierre
Meurer Gerhardt R.
Napiwotzki Ralf
Saffer Rex
Seibert Marvin M.
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