Radial velocity confirmation of K2-100b: a young, highly irradiated, and low-density transiting hot Neptune
Tamura, M.; Aigrain, S.; Pagano, I.; Barragán, O.; Gandolfi, D.; Fossati, L.; Korth, J.; Antoniciello, G.; Grziwa, S.; Albrecht, S.; Hatzes, A. P.; Cabrera, J.; Narita, N.; Cochran, W. D.; Kubyshkina, D.; Palle, E.; Persson, C. M.; Nowak, G.; Bedin, L. R.; Piotto, G.; Deeg, H. J.; Luque, R.; Redfield, S.; Granata, V.; Nardiello, D.; Latham, D. W.; Malavolta, L.; Zicher, N.; Murgas, F.; Fukui, A.; Parviainen, H.; Kusakabe, N.; Libralato, M.; Guenther, E.; Livingston, J.; Rajpaul, V. M.; de Leon, J.; Eigmüller, Ph; Montañés-Rodríguez, P.; Fridlund, M. C. V.
United Kingdom, Austria, Italy, Japan, Sweden, Netherlands, Germany, Spain, Denmark, United States
Abstract
We present a detailed analysis of HARPS-N radial velocity observations of K2-100, a young and active star in the Praesepe cluster, which hosts a transiting planet with a period of 1.7 d. We model the activity-induced radial velocity variations of the host star with a multidimensional Gaussian Process framework and detect a planetary signal of 10.6 ± 3.0 {m s^{-1}}, which matches the transit ephemeris, and translates to a planet mass of 21.8 ± 6.2 M⊕. We perform a suite of validation tests to confirm that our detected signal is genuine. This is the first mass measurement for a transiting planet in a young open cluster. The relatively low density of the planet, 2.04 _{ - 0.61 } ^ { + 0.66 } {g cm^{-3}}, implies that K2-100b retains a significant volatile envelope. We estimate that the planet is losing its atmosphere at a rate of 10^{11}-10^{12} {g s^{-1}} due to the high level of radiation it receives from its host star.