K2-99 revisited: a non-inflated warm Jupiter, and a temperate giant planet on a 523-d orbit around a subgiant

Kurzfassung

We report new photometric and spectroscopic observations of the K2-99 planetary system. Asteroseismic analysis of the short-cadence light curve from K2's Campaign 17 allows us to refine the stellar properties. We find K2-99 to be significantly smaller than previously thought, with a radius 2.55 ± 0.02 times that of the Sun. The new light curve also contains four transits of K2-99 b, which we use to improve our knowledge of the planetary properties. We find the planet to be a non-inflated warm Jupiter, with a radius 1.04 ± 0.01 times that of Jupiter. Fifty-eight new radial velocity measurements from HARPS, HARPS-N, and HIRES enable the determination of the orbital parameters of K2-99 c, which were previously poorly constrained. We find that this outer planet has a minimum mass of 8.4 ± 0.1 Jupiter masses , and an eccentric (0.205 ± 0.009) orbit with a period of 523 ± 2 d. Upcoming TESS observations in 2022 have a good chance of detecting the transit of this planet, if the mutual inclination between the two planetary orbits is small.