Journal. The Astrophysical Journal
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⊙, 3.19R⊙) but close masses (1.76M⊙, 1.79M⊙) and effective temperatures (7026K, 6902K), 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 δ Scuti type pulsations which we interpret as p-modes and p and g mixed modes. After a close examination of the evolution of δ Scuti pulsational frequencies, we make a comparison of the observed frequencies with those calculated from MESA/GYRE.
