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Asteroseismic modelling and orbital analysis of the triple star system HD 188753
Frédéric Marcadon (IAS), T. Appourchaux (IAS), J. P. Marques (IAS)
HD 188753 (HIP 98001, HO 581 or KIC 6469154) is known as a close visual binary discovered by Hough in 1895 and characterized by an orbital period of 25.7 years. In the late 1970s, it was established that the secondary is itself a spectroscopic binary with a period of 155 days. HD 188753 is therefore a hierarchical triple star system consisting of a close pair (Ba and Bb) in orbit at a distance of 12.3 AU from the primary (A). The triple star system was observed by Kepler in short-cadence mode during quarters Q13 and Q14. We report in this study the detection of solar-like oscillations for the brightest star HD 188753A. We perform the first asteroseismic analysis of HD 188753A using state-of-the-art stellar models in order to derive its fundamental parameters. We obtain the age and initial chemical composition of the star, which are assumed to be the same for the three members of the system, as well as a precise but model-dependent estimate of its mass. We then combine micrometric, interferometric and radial velocity measurements from almost a century of observations to determine the orbital masses of the three stars. We get direct constraint on the mass of HD 188753A which allows us to test different input physics in our stellar models. The full characterization of the triple stars HD 188753 is essential for better understanding the formation mechanisms and evolutionary processes of binaries and multiple stellar systems in our Galaxy.