Two extreme contact binary systems in the nearest globular cluster M4

Abstract

We present the results of photometric solutions for two contact binaries in the nearby globular cluster M4. We estimate their physical parameters using the light-curve program of the Wilson-Devinney code. These systems have quite different mass ratios, which indicates that they did not form at the same time. V47 is an extreme mass-ratio system (q = 0.123 ± 0.002) being dissimilar to the same kind of field contact binaries. V53 is a high mass-ratio (q = 1.230 ± 0.004), deep-contact (f = 79.7 ± 1.9 per cent) system. It is also a blue straggler.