Dr David Moriarty was the author on this publication in the Journal of the American Association of Variable Star Observers in 2016.


BC Gruis is a W UMa-type contact binary system of the W-subtype with the primary minimum 0.1 magnitudes fainter than the secondary minimum. The period is currently 0.3073060 ± 0.0000001 days; it was 7 seconds longer between 1986 and 1991. There were small modulations of 0.001 – 0.002 days in the Observed–Calculated diagram due to asymmetry in the light curves, most likely caused by star spots. An astrophysical model of the system was developed with a mass ratio of 1.2 determined from light curve analysis. The best fit to light curves in B, V and I pass bands in 2014 was given by including 2 large cool star spots on the more massive, cooler component and 1 cool spot on the hotter star. In 2015, the asymmetry in the light curves was different and was modelled best with a hot spot on the more massive component at the neck joining the stars and 1 cool spot on the other component.

The model has been updated with radial velocity data. Models of several of the binary systems have been prepared with Binary Maker; the Sun is shown as an orange circle to the scale of each binary system. View the model animation here:


Moriarty, D.J.W. 2016.
Period Analysis, Photometry and Astrophysical Modelling of the Contact Eclipsing Binary BC Gruis. Journal of the American Association of Variable Star Observers. 44: 10-17.
Web site: https://app.aavso.org/jaavso/article/3169/

Link to Publication