An Optical Study of BG Geminorum: An Ellipsoidal Binary with an Unseen Primar Star
Abstract
We describe optical photometric and spectroscopic observations of the bright variable BG Geminorum. Optical photometry shows a pronounced ellipsoidal variation of the K0 I secondary, with amplitudes of ~0.5 mag at VRI and a period of 91.645 days. A deep primary eclipse is visible for wavelengths < 4400A; a shallower secondary eclipse is present at longer wavelengths. Eclipse timings and the radial velocity curve of the K0 secondary star indicate an interacting binary where a lobe-filling secondary, M_2 ~ 0.5 Msun, transfers material into a extended disk around a massive primary, M_1 ~ 4.5 Msun. The primary star is either an early B-type star or a black hole. If it did contain a black hole, BG Gem would be the longest period black hole binary known by a factor of 10, as well as the only eclipsing black hole binary system.
Cite
@article{arxiv.astro-ph/9911179,
title = {An Optical Study of BG Geminorum: An Ellipsoidal Binary with an Unseen Primar Star},
author = {P. J. Benson and A. Dullighan and A. Bonanos and K. K. McLeod and S. J. Kenyon},
journal= {arXiv preprint arXiv:astro-ph/9911179},
year = {2009}
}
Comments
27 pages, includes 8 figures and 5 tables, accepted to AJ