Letter to the Editor

Dynamical mass of a solar-like oscillator at the main sequence turnoff from Gaia astrometry and ground-based spectroscopy

¹ Instit. de Astrofísica de Canarias E38205 La Laguna Tenerife, Spain
² Departamento de Astrofísica, Univ. de La Laguna Tenerife, Spain
³ Department of Physics, Faculty of Science, Univ. of Zagreb Zagreb, Croatia
⁴ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM 91191 Gif-sur-Yvette, France
⁵ École CentraleSupélec, Univ. Paris-Saclay Gif-sur-Yvette, France
⁶ Astronomical Institute, Faculty of Mathematics and Physics, Charles University V Holešovičkách 2 180 00 Prague, Czech Republic
⁷ Astrophysics Group, School of Physics and Astronomy, University of Exeter Stocker Road Exeter EX4 4QL, UK
⁸ IRAP, Université de Toulouse, CNRS, CNES, UPS 14 Avenue Edouard Belin 31400 Toulouse, France

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 27 September 2025
Accepted: 17 January 2026

Abstract

Asteroseismology is widely used for the precise mass determination of solar-like oscillating stars, based on individual frequency modeling or homological scaling relations. However, these methods have not been dynamically validated on the main sequence (MS) due to the absence of eclipsing double-lined binary system (SB2) as benchmark objects. By providing the orbital inclination, astrometric binary systems from ESA Gaia DR3 offer an abundant alternative for eclipsing systems. We present KIC 9693187 as the first SB2 hosting a solar-like oscillating post-MS star with dynamical masses. By combining Gaia astrometry with spectroscopic data obtained with the Las Cumbres Observatory network (LCO), we found M₁^dyn = 0.99 ± 0.05 M_⊙ and M₂^dyn = 0.89 ± 0.04 M_⊙ for the primary and secondary, respectively. The asteroseismic parameters were extracted from photometry of the NASA Kepler satellite. The mass from individual frequency modeling is M₁^IF = 0.92 ± 0.01 M_⊙. Taking into account the systematic uncertainty of 0.04 M_⊙ for best-fit models from individual frequency fitting, we found an agreement within 1.2σ. From the scaling relations, we obtained a mass range of 0.93 to 0.98 M_⊙ by using the observed large frequency separations (Δν) in the scaling relations for the primary. By using standard corrections for departures from the asymptotic regime of Δν, we obtained a mass range of 0.83 to 1.03 M_⊙. The upper ends of both ranges agree well with the dynamical mass of the primary. This approach provides the first empirical validation for MS solar-like oscillators and opens a new window for validating the asteroseismology. Through a dedicated program targeting astrometric SB2 binary systems, ESA’s PLATO space mission will effectively enlarge the benchmark sample to a considerable extent.