The Investigation of Seven Kepler Contact Binaries in the Field of NGC 6819

Abstract

Using the Kepler Eclipsing Binary Catalog, we found seven EW-type eclipsing binaries within the tidal radius of the intermediate-aged open cluster NGC 6819 (about 40'). These seven EW eclipsing binaries are all confirmed to be contact binaries by light curve analysis with the 2015 version Wilson-Devinney program. Using the parameter characteristics of contact binaries, we found that only KIC 4937217 could be a member of NGC 6819. Moreover, KIC 5199489 should be a shallow, unity-mass-ratio contact binary implying an early contact stage or a mass-ratio reverse stage. Nevertheless, KIC 5198934 and KIC 5374883 should be deep, low mass ratio contact binaries (DLMRCBs), which are usually considered as premergers.