2010PASP..122..309Z

This paper presents the first multicolor photometry of the neglected eclipsing binary KQ Gem. The light curves were obtained at the Xinglong Station of the National Astronomical Observatories, China in two observing runs: 2008 November 24-27, and 2008 December 31. With the 2003 version of the Wilson-Devinney program, these data were analyzed together with a light curve and some spectroscopic observations obtained by Hilditch and colleagues in 1992. Photometric solutions of KQ Gem are derived on the basis of the hot-spot model due to mass transfer via a stream hitting the facing surface of the secondary component. Our result confirms that KQ Gem is a marginal-contact binary system with a large temperature difference of about 1859 K between the two components. There is little variation among the curves from the three runs. This indicates a small variability for the hot spots on both a short and long time scale. Furthermore, the first orbital period analysis shows a probable period decrease based on all available primary times of light minimum, which could be explained by mass transfer or by magnetic braking. As the period decreases, KQ Gem will contact again and evolve into an overcontact system.