BG Geminorum

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BG Geminorum
Satellite image of binary star system BG Geminorum

Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Gemini
Right ascension 06h 03m 30.81s[1]
Declination +27° 41′ 50.7″[1]
Apparent magnitude (V) ~+14[2]
Spectral type K0I[3]
Distance 7340 ly
(2.25±0.25[3] pc)
Period (P) 91.645 days
Semi-major axis (a) >0.63 ± 0.04 AU
Inclination (i) >80°
Mass >3.5/>0.7[2] M
Temperature ???/4500[3] K

BG Geminorum is long period eclipsing binary star system which contains a K0 I secondary star in orbit around a primary star. The primary star has a mass at least 3.5 times that of the sun and could either be a B star (see Stellar Classification) or a black hole. Material from the K0 star is transferred to an accretion disk surrounding the unidentified primary star.


BG Gem was first observed by Hoffmeister (1933) and Jensch (1938) - initially an RV Tau star candidate with an uncertain period of ~ 60 days and a photographic magnitude of ~ 14. Until 1992, BG Gem remained in the General Catalog of Variable Stars (GCVS), when Benson et al. (2000) discovered an ellipsoidal variation with an optical magnitude of about 0.5, and improved the accuracy of the period to 91.645 days. Using light curves, a deep primary eclipse was revealed at shorter wavelengths (less than 4400Å), and a shallow eclipse at longer wavelengths.[3]

External links[edit]


  1. ^ a b Database entry for BG Geminorum, SIMBAD. Accessed online March 4, 2011.
  2. ^ a b Kenyon, Scott J; et al. (2002-05-10). "The Eclipsing Binary BG Geminorum: Improved Constraints on the Orbit and the Structure of the Accretion Disk". Retrieved 2011-03-04. 
  3. ^ a b c d e Benson, Priscilla J; et al. (1999-11-10). "An Optical Study of BG Geminorum: An Ellipsoidal Binary with an Unseen Primary Star". Retrieved 2011-03-04.