Radial velocity confirmation of K2-100b: a young, highly irradiated, and low density transiting hot Neptune
2019
We present a detailed analysis of
HARPS-N
radial velocityobservations of K2-100, a young and active star in the Praesepe cluster, which hosts a transiting
planetwith a period of 1.7 days. We model the activity-induced
radial velocityvariations of the host star with a multi-dimensional Gaussian Process framework and detect a planetary signal of $10.6 \pm 3.0 {\rm m\,s^{-1}}$, which matches the transit
ephemeris, and translates to a
planetmass of $21.8 \pm 6.2 M_\oplus$. We perform a suite of validation tests to confirm that our detected signal is genuine. This is the first mass measurement for a transiting
planetin a young
open cluster. The relatively low density of the
planet, $2.04^{+0.66}_{-0.61} {\rm g\,cm^{-3}}$, implies that K2-100b retains a significant volatile envelope. We estimate that the
planetis 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.
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