Asteroseismic grid-modelling of the binary system KIC 9163796

The age of a star cannot be measured but only inferred from observational quantities related to age. For stars in the red-giant phase, classical methods such as isochrone fitting can deliver ages with statistical uncertainties between 30% and 50%. Asteroseismic modelling is known to provide the most precise ages for red giants to date. Furthermore, modelling the observables provided by double-lined spectroscopic (SB2) binaries enables us to test the input physics and break parameter degeneracies. Combining asteroseismic constraints with those from dynamics offers a unique opportunity to improve the stellar parameters as well as the age of the system. In this talk, we present the results of the in-depth modelling analysis of KIC 9163796, an oscillating subgiant and red-giant SB2 binary system with almost identical masses, but with its components at significantly different positions in the HR diagram. Using a multi-dimensional grid computed with the stellar evolution code MESA, we modelled both binary components with different sets of observables. By exploiting the constraints from binarity, we test for the effect of the mixing-length parameter, initial helium, and the inclusion of the global seismic parameters on the joint stellar evolution. This yields an age estimation for the binary system of ~2 Gyr. We show that by combining asteroseismic and binarity constraints, the age uncertainty obtained from stellar modelling can be significantly decreased.