Photometric observations of an extreme mass ratio overcontact binary

Our R_C and I_C light curves of CSS J135012.1+272259 were analyzed with the Wilson-Devinney (W-D) program. The results reveal that CSS J135012.1+272259 is an extreme mass ratio overcontact binary with mass ratio q = 0.147. It may be in the final evolutionary stage of cool short-period binaries and merge into a single rapid-rotation star to form a blue straggler or FK Com type star. Also, 25 extreme mass ratio overcontact binary systems (q ≤ 0.15) are collected for long-term monitoring. These targets will improve understanding of the pre-outburst state of overcontact binaries and enrich knowledge of the merger mechanism.