Doppler confirmation of TESS planet candidate TOI−1408.01: grazing transit and likely eccentric orbit

Abstract

ABSTRACT We report an independent Doppler confirmation of the TESS planet candidate orbiting an F-type main-sequence star TOI−1408 located 140 pc away. We present a set of radial velocities obtained with a high-resolution fibre-optic spectrograph FFOREST mounted at the SAO RAS 6-m telescope (BTA-6). Our self-consistent analysis of these Doppler data and TESS photometry suggests a grazing transit such that the planet obscures its host star by only a portion of the visible disc. Because of this degeneracy, the radius of TOI−1408.01 appears ill-determined with lower limit about ∼1 RJup, significantly larger than in the current TESS solution. We also derive the planet mass of 1.69 ± 0.20 MJup and the orbital period ∼4.425 d, thus making this object a typical hot Jupiter, but with a significant orbital eccentricity of 0.259 ± 0.026. Our solution may suggest that the planet is likely to experience a high tidal eccentricity migration at the stage of intense orbital rounding, or may indicate possible presence of other unseen companions in the system, yet to be detected.