Advancing the accuracy in age determinations of old-disk stars using an oscillating red giant in an eclipsing binary

Context. The study of resonant oscillation modes in low-massred giant branch stars enables their ages to be inferred with exceptional (∼10%) precision, unlocking the possibility to reconstruct the temporal evolutionof the Milky Way at early cosmic times. Ensuring the accuracy of such a preciseage scale is a fundamental yet difficult challenge. Since the age of red giantbranch stars primarily hinges on their mass, an independent mass determinationfor an oscillating red giant star provides the means for such assessment.

Aims. We analyze the old eclipsing binary KIC 10001167, which hosts an oscillatingred giant branch star and is a member of the thick disk of the Milky Way. Ofthe known red giants in eclipsing binaries, this is the only member of thethick disk that has asteroseismic signal of high enough quality to test theseismic mass inference at the 2% level.

Methods. We measure the binary orbitand obtain fundamental stellar parameters through combined analysis of lightcurve eclipses and radial velocities, and perform a detailed asteroseismic,photospheric, and Galactic kinematic characterization of the red giant and binarysystem.

Results. We show that the dynamically determined mass 0.9337 ± 0.0077 M_⊙ (0.8%) of this 10 Gyr-old star agrees within 1.4% with the mass inferred fromdetailed modelling of individual pulsation mode frequencies (1.6%). This is nowthe only thick disk stellar system, hosting a red giant, where the mass hasbeen determined both asteroseismically with better than 2% precision, andthrough a model-independent method at 1% precision, and we hereby affirm thepotential of asteroseismology to define an accurate age scale for ancient starsto trace the Milky Way assembly history