A transiting warm giant planet around the young active star TOI-201

Abstract

We present the confirmation of the eccentric warm giant planet TOI-201 b, first identified as a candidate in \textit{TESS} photometry (Sectors 1-8, 10-13, and 27-28) and confirmed using ground-based photometry from NGTS and radial velocities from FEROS, HARPS, CORALIE, and \textsc{Minerva}-Australis. TOI-201 b orbits a young ($0.87_{-0.49}^{+0.46}\mathrm{Gyr}$) and bright(V=9.07 mag) F-type star with a $52.9781\mathrm{d}$ period. The planet has a mass of $0.42_{-0.03}^{+0.05}{\mathrm{M}}_{\mathrm{J}}$, a radius of $1.008_{-0.015}^{+0.012}{\mathrm{R}}_{\mathrm{J}}$, and an orbital eccentricity of $0.28_{-0.09}^{+0.06}$; it appears to still be undergoing fairly rapid cooling, as expected given the youth of the host star. The star also shows long-term variability in both the radial velocities and several activity indicators, which we attribute to stellar activity. The discovery and characterization of warm giant planets such as TOI-201 b is important for constraining formation and evolution theories for giant planets.

21 pages, 11 figures, accepted to AJ