Photometric light curve solutions of three ultra-short period eclipsing binaries

Acerbi, F.; Michel, R.; Barani, C.; Martignoni, M.; Fox-Machado, L.
eprint arXiv:1911.11802


We present the results of our study of the eclipsing binary systems CSS J112237.1+395219, LINEAR 1286561 and LINEAR 2602707 based on new CCD  and  complete light curves. The ultra-short period nature of the stars \citep{Drake2014} is confirmed and the system's periods are revised. The light curves were modelled using the 2005 version of the Wilson-Devinney code. When necessary, cool spots on the surface of the primary component were introduced to account for asymmetries in the light curves. As a result, we found that CSS J112237.1+395219 is a W UMa type contact binary system belonging to W subclass with a mass ratio of  and a shallow degree of contact of 14.8\% where the primary component is hotter than the secondary one by . LINEAR 1286561 and LINEAR 2602707 are detached binary systems with mass ratios  and  respectively. These detached systems are low-mass M-type eclipsing binaries of similar temperatures. The marginal contact, the fill-out factor and the temperature difference between components of CSS J112237.1+395219 suggest that this system may be at a key evolutionary state predicted by the Thermal Relaxation Oscillation theory (TRO). From the estimated absolute parameters we conclude that our systems share common properties with others ultra-short period binaries.