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

TL;DR

This study provides a comprehensive photometric and spectroscopic analysis of the contact binary KIC 7766185, revealing its classification, stellar parameters, and evidence of cyclic period variation, contributing to understanding of high mass ratio contact systems.

Contribution

It offers the first detailed analysis of KIC 7766185, including radial velocities, stellar parameters, and period variation, highlighting its unique large secondary star and shallow contact state.

Findings

Classified as an A-type W UMa system.

Identified one of the largest and most massive secondaries.

Detected cyclic variation in eclipse timings.

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.