A long-period transiting substellar companion in the super-Jupiters to brown dwarfs mass regime and a prototypical warm-Jupiter detected by TESS

Abstract

We report on the confirmation and follow-up characterization of two long-period transiting substellar companions on low-eccentricity orbits around TIC 4672985 and TOI-2529, whose transit events were detected by the TESS space mission. Ground-based photometric and spectroscopic follow-up from different facilities, confirmed the substellar nature of TIC 4672985 b, a massive gas giant in the transition between the super-Jupiters and brown dwarfs mass regime. From the joint analysis we derived the following orbital parameters: P = 69.0480-0.0005+0.0004 d, Mp = 12.74-1.01+1.01 Mj, Rp = 1.026-0.067+0.065 Rj and e = 0.018-0.004+0.004. In addition, the RV time series revealed a significant trend at the ~350 m s-1 yr-1 level, which is indicative of the presence of a massive outer companion in the system. TIC 4672985 b is a unique example of a transiting substellar companion with a mass above the deuterium-burning limit, located beyond 0.1 AU and in a nearly circular orbit. These planetary properties are difficult to reproduce from canonical planet formation and evolution models. For TOI-2529 b, we obtained the following orbital parameters: P = 64.5949-0.0003+0.0003 d, Mp = 2.340-0.195+0.197 Mj, Rp = 1.030-0.050+0.050 Rj and e = 0.021-0.015+0.024, making this object a new example of a growing population of transiting warm giant planets.