Three Saturn-mass planets transiting F-type stars revealed with TESS and HARPS

Abstract

While the sample of confirmed exoplanets continues to increase, 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 ($\sim$1277 $F_{\oplus }$) and bloated Saturn-mass planet (1.69${}_{-0.06}^{+0.05}$$R_{Jup}$ and 0.43${}_{-0.08}^{+0.09}$$M_{Jup}$) in a 4.66 day orbit transiting a 6850 K star. TOI-622b has a radius of 0.82${}_{-0.03}^{+0.03}$$R_{Jup}$ and a mass of 0.30${}_{-0.08}^{+0.07}$~$M_{Jup}$ in a 6.40 day orbit. Despite its high insolation flux ($\sim$600 $F_{\oplus }$), TOI-622b does not show any evidence of radius inflation. TOI-2641b is a 0.39${}_{-0.04}^{+0.02}$$M_{Jup}$ 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}$$R_{Jup}$. Additionally, TOI-615b is considered attractive for atmospheric studies via transmission spectroscopy with ground-based spectrographs and $\text{JWST}$. 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.

16 pages, 17 figures, submitted to A&A