Kepler Eclipsing Binaries with $\delta$ Scuti/$\gamma$ Doradus Pulsating Components 1: KIC 9851944

TL;DR

This study analyzes the binary star system KIC 9851944, combining Kepler photometry and spectra to determine stellar parameters, evolutionary stages, and pulsation modes, revealing complex stellar evolution and pulsation characteristics.

Contribution

It provides a detailed analysis of a pulsating eclipsing binary with combined observational and theoretical modeling, highlighting the evolutionary status and pulsation modes of both stars.

Findings

Primary star is on the main sequence with δ Scuti pulsations.

Secondary star has evolved to post-main sequence with mixed pulsation modes.

Model comparisons suggest solar metallicity and specific mass ratio fit the observed parameters.

Abstract

KIC 9851944 is a short period ($P=2.16$ days) eclipsing binary in the {\it Kepler} field of view. By combining the analysis of {\it Kepler} photometry and phase resolved spectra from Kitt Peak National Observatory and Lowell Observatory, we determine the atmospheric and physical parameters of both stars. The two components have very different radii ($2.27R_{\odot}$, $3.19R_{\odot}$) but close masses ($1.76 M_{\odot}$, $1.79M_{\odot}$) and effective temperatures ($7026$K, $6902$K), indicating different evolutionary stages. The hotter primary is still on the main sequence (MS), while the cooler and larger secondary star has evolved to post-MS, burning hydrogen in a shell. A comparison with coeval evolutionary models shows that it requires solar metallicity and a higher mass ratio to fit the radii and temperatures of both stars simultaneously. Both components show $\delta$ Scuti type pulsations which we interpret as p-modes and p and g mixed modes. After a close examination of the evolution of $\delta$ Scuti pulsational frequencies, we make a comparison of the observed frequencies with those calculated from MESA/GYRE.