Photometric investigation of the deep-contact binary V409 Hya

•The photometric solutions suggest V409 Hya is a low-mass ratio, deep contact binary.•Its orbital period is increasing.•V409 Hya may finally evolve into a rapidly rotating single star.

V409 Hya is a newly discovered W UMa-type binary star with a period of 0.47226 days. Complete light curves in V, RcRc, and IcIc bands are presented and analyzed with the W–D (Wilson and Devinney) method. It is discovered that V409 Hya is a deep contact binary with a contact degree of f=60.6(±1.4)%f=60.6(±1.4)%. It is an A-type, low-mass-ratio contact binary with a mass ratio of 0.22. The derived orbital inclination (i=89.8°i=89.8°) indicates that it is a total eclipsing binary and the determined parameters are reliable. By combining several determined times of light minimum with the others compiled from the literature, the period changes of V409 Hya were investigated. The general trend of the (O–C  ) curve reveals that the period of the binary is increasing continuously at a rate of dP/dt=+5.41(±0.06)×10-7dP/dt=+5.41(±0.06)×10-7 days/year. The continuous period increase can be explained by a mass transfer from the secondary to the primary. As the matter is being transferred, the mass ratio of the binary system is decreasing. After it meets the more familiar criterion that the orbital angular momentum is less than 3 times the total spin angular momentum, the deep contact binary may finally evolve into a rapid-rotating single star.