Radial velocity confirmation of K2-100b: a young, highly irradiated, and low-density transiting hot Neptune
/ Authors
O. Barrag'an, S. Aigrain, D. Kubyshkina, D. Gandolfi, J. Livingston, M. Fridlund, M. Fridlund, L. Fossati, J. Korth, H. Parviainen
and 39 more authors
H. Parviainen, L. Malavolta, E. Pallé, E. Pallé, H. Deeg, H. Deeg, G. Nowak, G. Nowak, V. Rajpaul, N. Zicher, G. Antoniciello, N. Narita, S. Albrecht, L. Bedin, J. Cabrera, W. Cochran, J. D. Leon, P. Eigmüller, A. Fukui, V. Granata, S. Grziwa, E. Guenther, A. Hatzes, N. Kusakabe, D. Latham, M. Libralato, R. Luque, R. Luque, P. Montañés-Rodríguez, P. Montañés-Rodríguez, F. Murgas, F. Murgas, D. Nardiello, Isabella Pagano, G. Piotto, C. Persson, C. Persson, S. Redfield, Motohide Tamura
/ 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 ${\rm m\, s^{-1}}$, 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, $2.04 _{ - 0.61 } ^ { + 0.66 }$ ${\rm g\, cm^{-3}}$, implies that K2-100b retains a significant volatile envelope. We estimate that the planet is losing its atmosphere at a rate of $10^{11}\!-\!10^{12}\, {\rm g\, s^{-1}}$ due to the high level of radiation it receives from its host star.
Journal: Monthly Notices of the Royal Astronomical Society