The first photometric investigation of the poor-thermal contact binary V749 Aurigae

Abstract

The multi-filter light curve analysis of V749 Aurigae (thereinafter V0749 Aur) is conducted for the first time. Its orbital period is improved from P = 0.409873 to 0.409890 d in this work. The photometric data from the All-Sky Automated Survey for SuperNovae (ASAS-SN) were utilized to examine the revised orbital period. Then, the phased multi-filter light curves were computed with the new period, and analyzed with the Wilson-Devinney (W-D) code. The results reveal that V0749 Aur is a marginal contact binary with a large temperature difference of about ΔT = 1600 K. It is a poor thermal contact binary, the light curves of which depart from EW-type and show EB-type light variations. Thus, V0749 Aur belongs to a particular group of binaries, named B-type binaries, predicted by the Thermal Relaxation Oscillation (TRO) theory. In addition, the amplitude differences in different bands of the light curves, imply the existence of a third light. The contribution of the third light detected by the light curve analysis is consistent with the contribution of a visual star, which is in the same line of sight as V0749 Aur but at a different distance. With its marginal contact and short period properties, V0749 Aur merits further attention as a potential transitional sample in binary evolution.