CCD photometric study of a contact binary HH Ursae Majoris

New complete BV light curves of a poorly investigated contact binary HH Ursae Majoris (HH UMa) are presented. The light curves are analyzed by using the 2003 version of the Wilson–Devinney (W–D) code. Combining with the radial velocity published by the previous investigators, we obtain the photometric solution of the system. The solution indicates that HH UMa is a W-type W UMa system with a mass ratio of q=m2/m1=3.344q=m2/m1=3.344 and a contact degree of 31.9%. The system has a very low inclination of i=53.035°i=53.035° and a temperature difference of 247 K between two components. The asymmetry of the light curves can be explained by adding a hot spot located near the neck region of the more massive component. A period investigation based on all available data shows that the period increases at a rate of dP/dt=2.84×10-7dP/dt=2.84×10-7 days yr−1, which can be explained by mass transfer from the less massive component to the more massive one. We also give the absolute parameters of the system.