The TASSIE Program. II: Three Close-In Companions Orbiting Sun-Like Stars

Abstract

We present three southern transiting giant planet candidates alerted by the Transiting Exoplanet Survey Satellite ( TESS ) mission and investigated at the University of Tasmania Greenhill Observatory (UTGO). The candidate planets are orbiting thin disk G-dwarf main-sequence stars with roughly solar metallicity, possessing orbital periods between 2.9 - 3.3 days and radii of 1.1 - 1.3 R J . We performed ground-based follow-up photometry primarily with the UTGO Harlingten 50 cm, then gathered reconnaissance spectra, high angular resolution imaging and high-precision radial velocities to rule out false positive scenarios. We confirmed that two of these systems host true exoplanets and constrained their masses. TOI-3053b is a typical hot Jupiter, with M 3053 b = 0.85 ± 0.12 M J and a bulk density of ρ 3053 b = 0.64 ± 0.10 g cm –3 . TOI-3278b/HATS-78b is a hot Saturn-mass planet ( M 3278 b = 0.30 ± 0.07 M J ) with a highly inflated atmosphere and a low density of ρ 3278 b = 0.21 ± 0.05 g cm –3 . The other candidate (TOI-3272.01) remains unconfirmed, but appears consistent with being a hot Jupiter. TOI-3272.01 is notable as a candidate planet orbiting a potentially young to intermediate age star, with a rotational analysis indicating an age estimate of T 3272 = 1.1 ± 0.2 Gyr. These systems add to a growing sample of hot giant planets from TESS that may provide constraints on the migration pathways and radius inflation of the broader close-in exoplanet population.