KIC 9028474: A Long-period Eclipsing Binary on a Highly Eccentric Orbit

Abstract

We present a comprehensive analysis of a very long-period (124.93669 days) eclipsing binary KIC 9028474, which is composed of F9V+G1V components on a highly eccentric (e = 0.82029) orbit. Masses and radii of the primary and the secondary components are M 1 = 1.18 ± 0.04 M ⊙, M 2 = 1.04 ± 0.03 M ⊙, R 1 = 1.52 ± 0.02 R ⊙, and R 2 = 1.11 ± 0.01 R ⊙, respectively. Eclipse time variations show the presence of apsidal motion, which in turn shows the existence of a third body in a relatively close orbit. Simultaneous analysis of infrared spectra and space photometry reveals that the primary component is about to leave the main sequence, indicating an age of 5.2 ± 0.8 Gyr for the system. Theoretical evaluation of the observed eccentricity indicates that the components of KIC 9028474 will end their whole life much before the orbital circularization is achieved. Given the limited resolution of the spectra, we can only place an upper limit on the rotational velocities of each star, thus a theoretical evaluation of the synchronization of the components.