A Transiting Warm Giant Planet around the Young Active Star TOI-201

We present the confirmation of the eccentric warm giant planet TOI-201 b, first identified as a candidate in Transiting Exoplanet Survey Satellite photometry (Sectors 1-8, 10-13, and 27-28) and confirmed using ground-based photometry from Next Generation Transit Survey and radial velocities from FEROS, HARPS, CORALIE, and 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 day period. The planet has a mass of ${0.42}_{-0.03}^{+0.05}\,{M}_{{\rm{J}}}$ , a radius of ${1.008}_{-0.015}^{+0.012}\,{R}_{{\rm{J}}}$ , 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 are important for constraining formation and evolution theories for giant planets.