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 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 Minerva-Australis. TOI-201 b orbits a young (\(0.87^{+0.46}_{-0.49}\) Gyr) and bright(V=9.07 mag) F-type star with a 52.9781 d period. The planet has a mass of \(0.42^{+0.05}_{-0.03}\) M\(_\mathrm{J}\), a radius of \(1.008^{+0.012}_{-0.015}\) R\(_\mathrm{J}\), and an orbital eccentricity of \(0.28^{+0.06}_{-0.09}\); 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.

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