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Astronomy & Astrophysics manuscript no. 0917 January 27, 2004 (DOI: will be inserted by hand later)

Summary: Astronomy & Astrophysics manuscript no. 0917 January 27, 2004
(DOI: will be inserted by hand later)
Discovery of a spectroscopic binary comprising two hot
helium-rich subdwarfs
A. Ahmad1, C. S. Jeffery1, and A. W. Fullerton2,3
Armagh Observatory, College Hill, Armagh BT61 9DG. N. Ireland. UK
Dept. of Physics and Astronomy, University of Victoria, PO Box 3055, Victoria, BC V8W 3P6, Canada
Dept. of Physics and Astronomy, The Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
Received 22 December 2003 / Accepted 17 January 2004
Abstract. Helium-rich subdwarf B (He-sdB) stars form a very small fraction of the population of hot subdwarf stars in our
Galaxy. They have been found both in the field of our Galaxy as well as in globular clusters. The evolution of these rare stars has
recently been the subject of much debate involving both binary and single star evolution models. We report our serendipitous
discovery that the prototype PG 1544+488 is a binary containing two low-mass helium-rich hot subdwarfs. This discovery
challenges existing evolutionary models for He-sdB stars and suggests that they may be formed through close binary evolution
and following the ejection of a common envelope.
Key words. stars: chemically peculiar - stars: early-type - subdwarfs - stars: individual : PG 1544+488 - stars: fundamental
parameters - binaries: spectroscopic


Source: Armagh Observatory


Collections: Physics