Improving the stellar age determination through joint modeling of binarity and asteroseismology

Grid modeling of the seismic red giant binary KIC 9163796

¹ Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife, Spain
² Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain
³ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Straße 1, 85741 Garching bei München, Germany
⁴ Department of Astrophysics, IMAPP, Radboud University Nijmegen, PO Box 9010 6500 GL Nijmegen, The Netherlands
⁵ Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
⁶ Department of Physics and Astronomy, California State University, Long Beach, Long Beach, CA 90840, USA
⁷ INAF – Osservatorio Astronomico d’Abruzzo, Via M. Maggini sn., Teramo, Abruzzo, Italy
⁸ INFN – Sezione di Pisa, Largo Pontecorvo 3, 56127 Pisa, Italy
⁹ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
¹⁰ Institut für Physik, Karl-Franzens Universität Graz, Universitätsplatz 5/II, NAWI Graz, 8010 Graz, Austria
¹¹ Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006, Australia
¹² Graz University of Technology, Rechbauerstraße 12, Graz, Austria
¹³ School of Physics, University of New South Wales, Sydney NSW 2052, Australia

^⋆ Corresponding author; desmond.grossmann@iac.es

Received: 15 October 2024
Accepted: 14 January 2025

Abstract

Context. The typical uncertainties of ages determined for single star giants from isochrone fitting using single-epoch spectroscopy and photometry without any additional constraints are 30–50%. Binary systems, particularly double-lined spectroscopic binaries, provide an opportunity to study the intricacies of internal stellar physics and better determine stellar parameters, particularly stellar age.

Aims. By using the constraints from binarity and asteroseismology, we aim to obtain precise age and stellar parameters for the red giant-subgiant binary system KIC 9163796, a system with a mass ratio of 1.015 but distinctly different positions in the Hertzsprung–Russell diagram.

Methods. We computed a multidimensional model grid of individual stellar models. From different combinations of figures of merit, we used the constraints drawn from binarity, spectroscopy, and asteroseismology to determine the stellar mass, chemical composition, and age of KIC 9163796.

Results. Our combined-modeling approach leads to an age estimation of the binary system KIC 9163796 of 2.44_−0.20^+0.25 Gyr, which corresponds to a relative error in the age of 9%. Furthermore, we found both components exhibit an equal initial helium abundance of 0.27 to 0.30, which is significantly higher than the primordial helium abundance, and an initial heavy metal abundance below the spectroscopic value. The masses from our models are in agreement with the masses derived from the asteroseismic scaling relations.

Conclusions. By exploiting the distinct positions of the components of KIC 9163796, we successfully demonstrate that combining asteroseismic and binary constraints leads to a significant improvement in the precision of age estimation, resulting in a relative error in age below 10% for a giant star.