Three Saturn-mass planets transiting F-type stars revealed with TESS and HARPS: TOI-615b, TOI-622b, and TOI-2641b

Abstract

While the sample of confirmed exoplanets continues to grow, the population of transiting exoplanets around early-type stars is still limited. These planets allow us to investigate the planet properties and formation pathways over a wide range of stellar masses and study the impact of high irradiation on hot Jupiters orbiting such stars. We report the discovery of TOI-615b, TOI-622b, and TOI-2641b, three Saturn-mass planets transiting main sequence, F-type stars. The planets were identified by the Transiting Exoplanet Survey Satellite (TESS) and confirmed with complementary ground-based and radial velocity observations. TOI-615b is a highly irradiated (∼1277 F) and bloated Saturn-mass planet (1.69-0.06+0.05 RJup and 0.43-0.08+0.09 MJup) in a 4.66 day orbit transiting a 6850 K star. TOI-622b has a radius of 0.82-0.03+0.03 RJup and a mass of 0.30-0.08+0.07 MJup in a 6.40 day orbit. Despite its high insolation flux (∼600 F), TOI-622b does not show any evidence of radius inflation. TOI-2641b is a 0.39-0.04+0.02 MJup planet in a 4.88 day orbit with a grazing transit (b = 1.04-0.06+0.05) that results in a poorly constrained radius of 1.61-0.64+0.46 RJup. Additionally, TOI-615b is considered attractive for atmospheric studies via transmission spectroscopy with ground-based spectrographs and JWST. Future atmospheric and spin-orbit alignment observations are essential since they can provide information on the atmospheric composition, formation, and migration of exoplanets across various stellar types.