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

James S. Kuszlewicz, Thomas S. H. North, William J. Chaplin, Allyson Bieryla, David W. Latham, Andrea Miglio, Keaton J. Bell, Guy R. Davies, Saskia Hekker, Tiago L. Campante, Sebastien Deheuvels, Mikkel N. Lund

KOI-3890: A high mass-ratio asteroseismic red-giant$+$M-dwarf eclipsing binary undergoing heartbeat tidal interactions See arXiv version 11 pages, 5 figures, accepted for publication in MNRAS


KOI-3890 is a highly eccentric, 153-day 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 have enabled the detailed characterisation 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 \(M_{\star}=1.04\pm0.06\;\textrm{M}_{\odot}\) and \(R_{\star}=5.8\pm0.2\;\textrm{R}_{\odot}\) respectively. When combined with transit photometry the M-dwarf companion is found to have a mass and radius of \(M_{\mathrm{c}}=0.23\pm0.01\;\textrm{M}_{\odot}\) and \(R_{\mathrm{c}}=0.256\pm0.007\;\textrm{R}_{\odot}\). Moreover, through asteroseismology we constrain the age of the system through the red-giant primary to be \(9.1^{+2.4}_{-1.7}\;\mathrm{Gyr}\). 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\textemdash the angle between the stellar rotation axis and the angle normal to the orbital plane\textemdash is also derived to give \(\psi=4.2^{+2.1}_{-4.2}\) 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.

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