Distribution of physical parameters for 380 contact binaries in the Kepler field

Abstract

We present the physical parameters (p, T, q, i, f) of 380 Kepler contact binary systems (hereafter called CBs). A statistical study on the CBs is carried out based on a Kepler photometric database. Our samples were selected from the Kepler Eclipsing Binary Catalogue of EW-type eclipsing binaries with periods around 0.2-1 d and amplitudes greater than $5\%$ . The physical parameters were obtained by fitting the Kepler light curves with the Wilson-Devinney eclipsing binary modeling program. Our sample of CBs contains 160 A-type and 220 W-type CBs. The fill-out factor distribution indicated that CBs generally have shallow fill-out; the proportion of CBs with fill-out factors less than $30\%$ is around $70\%$ , which may be related to the formation and evolution of the CBs. The period-temperature relationship of CBs is consistent with previous studies, which is the well-known period-color relationship. The distribution between mass ratio and fill-out factor can provide some information for studying the deep, low-mass ratio contact binaries and CBs which have a large mass ratio. The mass-radius diagram shows that there is a similar linear relationship between the primary and secondary stars while the primary stars are located almost on the ZAMS line; this could be related to the internal nuclear reaction within the primary and secondary stars.