Radial velocity confirmation of K2-100b : A young, highly irradiated, and low-density transiting hot Neptune

Summary, in English

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⁺₋⁰₀⁶⁶₆₁ 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 10¹¹–10¹² g s⁻¹ due to the high level of radiation it receives from its host star.

• Author: O. Barragán; S. Aigrain; D. Kubyshkina; D. Gandolfi; J. Livingston; M. C.V. Fridlund; L. Fossati; J. Korth; H. Parviainen; L. Malavolta; E. Palle; H. J. Deeg; G. Nowak; V. M. Rajpaul; N. Zicher; G. Antoniciello; N. Narita; S. Albrecht; L. R. Bedin; J. Cabrera; W. D. Cochran; J. De Leon; P. Eigmüller; A. Fukui; V. Granata; S. Grziwa; E. Guenther; A. P. Hatzes; N. Kusakabe; D. W. Latham; M. Libralato; R. Luque; P. Montañés-Rodríguez; F. Murgas; D. Nardiello; I. Pagano; G. Piotto; C. M. Persson; S. Redfield; M. Tamura
• Publishing year: 2019-11-21
• Language: English
• Pages: 698-708
• Publication/Series: Monthly Notices of the Royal Astronomical Society
• Volume: 490
• Issue: 1
• Links: http://dx.doi.org/10.1093/mnras/stz2569
• Document type: Journal article
• Publisher: Oxford University Press
• Keywords: Planets and satellites: individual: K2-100b; Techniques: photometric; Techniques: radial velocities
• Status: Published
• ISBN/ISSN/Other: ISSN: 0035-8711