V2769 Orionis: A new low-mass-ratio and deep-contact binary

Abstract

We carried out the first multi-color light curves analysis of the eclipsing binary V2769 Ori. The photometric solution was determined by applying the Wilson–Devinney method. The results show that V2769 Ori is a deep, low-mass-ratio contact binary with a mass ratio of q=0.162(±0.003) and a contact degree of f=55(±8)%. The total eclipse characteristics of V2769 Ori imply that the photometric solution we obtained is reliable. With all available light minimum times, the O–C diagram was constructed and analyzed. The orbital period analysis reveals a long-term period decrease at a rate of dP/dt=−1.24(±0.08)×10−6dyr−1 and a periodic oscillation with a period of 8.77(±0.15) years. The secular period decrease can be explained by a combination of mass transfer between the two components and the angular momentum loss of the system. As the orbital period decrease, the shrinking of the inner and outer critical Roche lobes causes an increase in contact degree, and the binary system will finally merge into a rapidly rotating single star. Periodic oscillation may be the result of the light-travel time effect due to the presence of an unseen component.