TIC 278825952: a Triply Eclipsing Hierarchical Triple System with the Most Intrinsically Circular Outer Orbit
MNRAS 000,1–10 (2020) Preprint 9 September 2020 Compiled using MNRAS LATEX style file v3.0 TIC 278825952: a triply eclipsing hierarchical triple system with the most intrinsically circular outer orbit T. Mitnyan,1?, T. Borkovits1;2;3, S. A. Rappaport4, A. Pál2;5, P. F. L. Maxted6 1Baja Astronomical Observatory of University of Szeged, H-6500 Baja, Szegedi út, Kt. 766, Hungary 2Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, H-1121 Budapest, Konkoly Thege Miklós út 15-17, Hungary 3 ELTE Gothard Astrophysical Observatory, H-9700 Szombathely, Szent Imre h. u. 112, Hungary 4 Department of Physics, Kavli Institute for Astrophysics and Space Research, M.I.T., Cambridge, MA 02139, USA 5 ELTE Eötvös Loránd University, Institute of Physics, H-1117 Budapest, Pázmány Péter stny. 1A Hungary 6 Astrophysics Group, Keele University, Staffordshire, ST5 5BG, UK Accepted XXX. Received YYY; in original form ZZZ ABSTRACT We report the discovery of a compact triply eclipsing triple star system in the southern con- tinuous viewing zone of the TESS space telescope. TIC 278825952 is a previously unstudied, circular eclipsing binary with a period of 4.781 days with a tertiary component in a wider, circular orbit of 235.55 days period that was found from three sets of third-body eclipses and from light travel-time effect dominated eclipse timing variations. We performed a joint photo- dynamical analysis of the eclipse timing variation curves, photometric data, and the spectral energy distribution, coupled with the use of PARSEC stellar isochrones. We find that the inner binary consists of slightly evolved, near twin stars of masses of 1.12 and 1.09 M and radii of 1.40 and 1.31 R .
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