Binary Analysis and Period Study of the Long-Period, High Mass Ratio Contact Binary KIC 7766185

Abstract

We present an in-depth photometric and spectroscopic study of the contact binary KIC 7766185. Spectroscopic observations were conducted on the Mayall 4-m telescope at Kitt Peak National Observatory and used to extract radial velocities. Using the radial velocity measurements, Kepler photometry, and Gaia multi-color photometry, binary analysis was performed in PHOEBE to determine orbital and stellar parameters. The results classify KIC 7766185 as an A-type W UMa system and reveal one of the largest and most massive secondary stars in the sample of well studied W UMa systems. The two stars are in a shallow contact state, with a small fillout factor of $0.029\pm0.002$. Along with the binary analysis, we conduct a period study that reveals evidence for a cyclic variation in the eclipse timings.