Open AccessAn Optical Study of BG Geminorum: An Ellipsoidal Binary with an Unseen Primary Star
Author(s) -
P. J. Benson,
A. Dullighan,
A. Z. Bonanos,
Kim K. McLeod,
Scott J. Kenyon
Publication year - 2000
Publication title -
the astronomical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.61
H-Index - 271
eISSN - 1538-3881
pISSN - 0004-6256
DOI - 10.1086/301230
Subject(s) - physics , astrophysics , eclipse , astronomy , primary (astronomy) , light curve , black hole (networking) , photometry (optics) , roche lobe , binary star , binary number , radial velocity , stars , computer network , routing protocol , routing (electronic design automation) , arithmetic , mathematics , computer science , link state routing protocol
We describe optical photometric and spectroscopic observations of the brightvariable BG Geminorum. Optical photometry shows a pronounced ellipsoidalvariation of the K0 I secondary, with amplitudes of ~0.5 mag at VRI and aperiod of 91.645 days. A deep primary eclipse is visible for wavelengths <4400A; a shallower secondary eclipse is present at longer wavelengths. Eclipsetimings and the radial velocity curve of the K0 secondary star indicate aninteracting binary where a lobe-filling secondary, M_2 ~ 0.5 Msun, transfersmaterial into a extended disk around a massive primary, M_1 ~ 4.5 Msun. Theprimary star is either an early B-type star or a black hole. If it did containa black hole, BG Gem would be the longest period black hole binary known by afactor of 10, as well as the only eclipsing black hole binary system.Comment: 27 pages, includes 8 figures and 5 tables, accepted to A
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