DZ Lyn: a contact binary with components in poor thermal contact

Abstract

CCD photometric observations of the short-period eclipsing binary DZ Lyn were obtained during seven nights in March–April 2008 in the B, V, Rc and Ic bands: these observations confirm the short-period (P = 0.378 d) of the system. The presented light curves are analyzed by means of the 2003 version of the Wilson–Devinney (WD) program. A grid of solutions for several fixed values of mass ratio was calculated. The best fitting possible is for a mass ratio of q = 0.885, a degree of contact f = 0.18 and a low orbital inclination of i = 57.6o. The results show that DZ Lyn is an A-subtype W Ursae Majoris contact binary in poor thermal contact; in fact the difference between the mean temperatures of the components is about 1800K. The star DZ Lyn seems to be another member of the class of poorly understood close binaries in or near geometrical contact but far from thermal contact. The absolute dimensions are estimated and its dynamical evolution is inferred.