2015AJ....150....9X

By analyzing R_c and I_clight curves of the short-period solar-type eclipsing binary GSC 1537-1557 we discovered that it is a shallow contact binary with a degree of contact factor of f = (8.1 ± 1.79)%. Photometric solutions reveal that GSC 1537-1557 is a W-type system with a mass ratio of q = M₂/M₁ = 2.645 where the less massive component (the primary star) is about 110 K hotter than the more massive one (the secondary star). The asymmetry and variation of the light curves were explained as the activity of spots on the solar-type component stars. By investigating all of the available times of light minima, we found that the observed-calculated (O-C) curve shows a cyclic variation with a small amplitude of 0.00335 days and a period of 8.1 years. The small-amplitude cyclic change in the O -C curve was analyzed for the light-travel time effect via the presence of an extremely cool stellar companion. The mass of the third body was determined to be M₃ sin i' = (0.19 ± 0.01) M_☉ when M₁ + M₂ = 1.31 M_☉ is adopted for GSC 1537-1557. The semimajor axis of the outer obit is a' sin i' = (4.58 ± 0.33) AU.