Photometric study of the contact binary 07g-3-00820 at the period cut off

07g-3-00820 is a K-type contact binary system with a period of 0.2269551 days. This extremely short period makes this system a rare target whose period is close to the empirical limit (0.22 days). Rc and Ic light curves of this binary were obtained using the 1.0 m reflecting telescope at Weihai Observatory of Shandong University. A high mass ratio of q = 1.300 ± 0.006 and a low contact degree of f = 5 % ± 1.5 % were determined from a photometric study using the Wilson–Devinney method. The following parameters of this W-subtype shallow contact system were derived: M 1 = 0.621 ± 0.072 M ⊙ , M 2 = 0.807 ± 0.093 M ⊙ , R 1 = 0.634 ± 0.036 R ⊙ , R 2 = 0.710 ± 0.037 R ⊙ , L 1 = 0.270 ± 0.037 L ⊙ , and L 2 = 0.339 ± 0.048 L ⊙ . By analyzing the location of the two components on the mass-luminosity diagram, we provide a preliminary discussion on the properties and the state of evolution of this system.