Absolute stellar parameters of KIC 09246715 -- a double-giant eclipsing system with a solar-like oscillator

TL;DR

This study precisely measures the stellar parameters of a rare double-giant eclipsing binary system, confirming the secondary's solar-like oscillations and validating asteroseismic results with independent methods.

Contribution

First precise measurement of both stars' masses and radii in a double-giant eclipsing binary with confirmed solar-like oscillations, validating asteroseismic analysis.

Findings

Masses and radii of both giants measured with <2% precision.

Confirmed the secondary's solar-like oscillations through independent analysis.

Validated asteroseismic parameters with direct measurements.

Abstract

We present our results of a combined analysis of radial velocity and light curves of a double-lined spectroscopic and eclipsing binary KIC 09246715, observed photometrically by the $Kepler$ satellite, and spectroscopically with the OAO-1.88m telescope with the HIgh-Dispertion Echelle Spectrograph (HIDES). The target was claimed to be composed of two red giants, one of which is showing solar-like oscillations. We have found that the mass and radius of the primary are $M_1=2.169\pm0.024$ M$_\odot$ and $R_1=8.47\pm0.13$ R$_\odot$, and of the secondary: $M_2=2.143\pm0.025$ M$_\odot$ and $R_2=8.18\pm0.09$ R$_\odot$, which confirms the double-giant status. Our secondary is the star to which the oscillations were attributed. Results of its previous asteroseismic analysis are in agreement with ours, only significantly less precise, but the subsequent light-curve-based study failed to derive correct mass and radius of our primary. KIC 09246715 is one of the rare cases where asteroseismic parameters of a solar-like oscillator were confirmed by an independent method, and only the third example of a Galactic double-giant eclipsing binary with masses and radii measured with precision below 2%.