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KOI-3890: a high-mass-ratio asteroseismic red giant+M-dwarf eclipsing binary undergoing heartbeat tidal interactions

J. S. Kuszlewicz, T. S. H. North, W. J. Chaplin, A. Bieryla, D. W. Latham, A. Miglio, K. J. Bell, G. R. Davies, S. Hekker, T. L. Campante, S. Deheuvels, M. N. Lund

Abstract
KOI-3890 is a highly eccentric, 153-d period eclipsing, single-lined spectroscopic binary system containing a red giant star showing solar-like oscillations alongside tidal interactions. The combination of transit photometry, radial velocity observations, and asteroseismology has enabled the detailed characterization of both the red giant primary and the M-dwarf companion, along with the tidal interaction and the geometry of the system. The stellar parameters of the red giant primary are determined through the use of asteroseismology and grid-based modelling to give a mass and radius of M=1.04±0.06M and R=5.8±0.2R⁠, respectively. When combined with transit photometry, the M-dwarf companion is found to have a mass and radius of Mc=0.23±0.01M and Rc=0.256±0.007R⁠. Moreover, through asteroseismology we constrain the age of the system through the red giant primary to be 9.1+2.4−1.7Gyr⁠. This provides a constraint on the age of the M-dwarf secondary, which is difficult to do for other M-dwarf binary systems. In addition, the asteroseismic analysis yields an estimate of the inclination angle of the rotation axis of the red giant star of i=87.6+2.4−1.2 degrees. The obliquity of the system – the angle between the stellar rotation axis and the angle normal to the orbital plane – is also derived to give ψ=4.2+2.1−4.2 degrees, showing that the system is consistent with alignment. We observe no radius inflation in the M-dwarf companion when compared to current low-mass stellar models.

Keywords
asteroseismology; techniques: photometric; binaries: eclipsing; stars: evolution; stars: fundamental parameters; Astrophysics - Solar and Stellar Astrophysics

Monthly Notices of the Royal Astronomical Society
Volume 487, Issue 1, Page 14
2019 May

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Instituto de Astrofísica e Ciências do Espaço Universidade do Porto Faculdade de Ciências da Universidade de Lisboa
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia