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Planet Hunters TESS I: TOI 813, a subgiant hosting a transiting Saturn-sized planet on an 84-day orbit

Abstract : We report on the discovery and validation of TOI 813 b (TIC 55525572 b), a transiting exoplanet identified by citizen scientists in data from NASA's Transiting Exoplanet Survey Satellite (TESS) and the first planet discovered by the Planet Hunters TESS project. The host star is a bright (V = 10.3 mag) subgiant (R\star - 1.94 R, M\star = 1.32 M). It was observed almost continuously by TESS during its first year of operations, during which time four individual transit events were detected. The candidate passed all the standard light curve-based vetting checks, and ground-based follow-up spectroscopy and speckle imaging enabled us to place an upper limit of 2 MJup (99 per cent confidence) on the mass of the companion, and to statistically validate its planetary nature. Detailed modelling of the transits yields a period of 83.8911-0.0031+0.0027 d, a planet radius of 6.71 ± 0.38 R and a semimajor axis of 0.423-0.037+0.031 AU. The planet's orbital period combined with the evolved nature of the host star places this object in a relatively underexplored region of parameter space. We estimate that TOI 813 b induces a reflex motion in its host star with a semi-amplitude of ∼6 m s-1, making this a promising system to measure the mass of a relatively long-period transiting planet.
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Contributor : Nathalie POTHIER Connect in order to contact the contributor
Submitted on : Friday, May 13, 2022 - 11:44:47 AM
Last modification on : Saturday, June 25, 2022 - 3:17:13 AM


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N. L. Eisner, O. Barragán, S. Aigrain, C. Lintott, G. Miller, et al.. Planet Hunters TESS I: TOI 813, a subgiant hosting a transiting Saturn-sized planet on an 84-day orbit. Monthly Notices of the Royal Astronomical Society, 2020, 494, pp.750-763. ⟨10.1093/mnras/staa138⟩. ⟨insu-03667101⟩



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