Abstract
Context. The NASA Kepler space telescope has detected solar-like oscillations in several hundreds of single stars, thereby providing a way to determine precise stellar parameters using asteroseismology. Aims. In this work, we aim to derive the fundamental parameters of a close triple star system, HD 188753, for which asteroseismic and astrometric observations allow independent measurements of stellar masses. Methods. We used six months of Kepler photometry available for HD 188753 to detect the oscillation envelopes of the two brightest stars. For each star, we extracted the individual mode frequencies by fitting the power spectrum using a maximum likelihood estimation approach. We then derived initial guesses of the stellar masses and ages based on two seismic parameters and on a characteristic frequency ratio, and modelled the two components independently with the stellar evolution code CESTAM. In addition, we derived the masses of the three stars by applying a Bayesian analysis to the position and radial-velocity measurements of the system. Results. Based on stellar modelling, the mean common age of the system is 10.8 ± 0.2 Gyr and the masses of the two seismic components are MA = 0.99 ± 0.01 M⊙ and MBa = 0.86 ± 0.01 M⊙. From the mass ratio of the close pair, MBb/MBa = 0.767 ± 0.006, the mass of the faintest star is MBb = 0.66 ± 0.01 M⊙ and the total seismic mass of the system is then Msyst = 2.51 ± 0.02 M⊙. This value agrees perfectly with the total mass derived from our orbital analysis, Msyst = 2.51−0.18+0.20 M⊙, and leads to the best current estimate of the parallax for the system, π = 21.9 ± 0.2 mas. In addition, the minimal relative inclination between the inner and outer orbits is 10.9° ± 1.5°, implying that the system does not have a coplanar configuration.
Highlights
Stellar physics has experienced a revolution in recent years with the success of the CoRoT (Baglin et al 2006) and Kepler space missions (Gilliland et al 2010a)
We aim to derive the fundamental parameters of a close triple star system, HD 188753, for which asteroseismic and astrometric observations allow independent measurements of stellar masses
The Kepler space telescope yielded unprecedented data allowing the detection of solar-like oscillations in more than 500 stars (Chaplin et al 2011) and the extraction of mode frequencies for a large number of targets (Appourchaux et al 2012b; Davies et al 2016; Lund et al 2017)
Summary
Stellar physics has experienced a revolution in recent years with the success of the CoRoT (Baglin et al 2006) and Kepler space missions (Gilliland et al 2010a). Using scaling relations, the measurement of the seismic parameters ∆ν and νmax provides a model-free estimate of stellar mass and radius (Chaplin et al 2011, 2014). A proper calibration of the evolutionary models and scaling relations is required in order to derive the stellar mass, radius, and age with a high-level of accuracy. In this context, binary stars provide a unique opportunity to check the consistency of the derived stellar quantities
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