K2-280b -- a low density warm sub-Saturn around a mildly evolved star
Abstract
We present an independent discovery and detailed characterisation of K2-280b, a transiting low density warm sub-Saturn in a 19.9-day moderately eccentric orbit (e = 0.35_{-0.04}^{+0.05}) from K2 campaign 7. A joint analysis of high precision HARPS, HARPS-N, and FIES radial velocity measurements and K2 photometric data indicates that K2-280b has a radius of R_b = 7.50 +/- 0.44 R_Earth and a mass of M_b = 37.1 +/- 5.6 M_Earth, yielding a mean density of 0.48_{-0.10}^{+0.13} g/cm^3. The host star is a mildly evolved G7 star with an effective temperature of T_{eff} = 5500 +/- 100 K, a surface gravity of log(g) = 4.21 +/- 0.05 (cgs), and an iron abundance of [Fe/H] = 0.33 +/- 0.08 dex, and with an inferred mass of M_star = 1.03 +/- 0.03 M_sun and a radius of R_star = 1.28 +/- 0.07 R_sun. We discuss the importance of K2-280b for testing formation scenarios of sub-Saturn planets and the current sample of this intriguing group of planets that are absent in the Solar System.
Keywords
Cite
@article{arxiv.2007.07939,
title = {K2-280b -- a low density warm sub-Saturn around a mildly evolved star},
author = {Grzegorz Nowak and Enric Palle and Davide Gandolfi and Hans J. Deeg and Teruyuki Hirano and Oscar Barragán and Masayuki Kuzuhara and Fei Dai and Rafael Luque and Carina M. Persson and Malcolm Fridlund and Marshall C. Johnson and Judith Korth and John H. Livingston and Sascha Grziwa and Savita Mathur and Artie P. Hatzes and Jorge Prieto-Arranz and David Nespral and Diego Hidalgo and Maria Hjorth and Simon Albrecht and Vincent Van Eylen and Kristine W. F. Lam and William D. Cochran and Massimiliano Esposito and Szilárd Csizmadia and Eike W. Guenther and Petr Kabath and Pere Blay and Rafael Brahm and Andrés Jordán and Néstor Espinoza and Felipe Rojas and Núria Casasayas Barris and Florian Rodler and Roi Alonso Sobrino and Juan Cabrera and Ilaria Carleo and Alexander Chaushev and Jerome de Leon and Philipp Eigmüller and Michael Endl and Anders Erikson and Akihiko Fukui and Iskra Georgieva and Lucía González-Cuesta and Emil Knudstrup and Mikkel N. Lund and Pilar Montañes Rodríguez and Felipe Murgas and Norio Narita and Prajwal Niraula and Martin Pätzold and Heike Rauer and Seth Redfield and Ignasi Ribas and Marek Skarka and Alexis M. S. Smith and Jano Subjak},
journal= {arXiv preprint arXiv:2007.07939},
year = {2020}
}
Comments
14 pages, 9 figures, 5 tables, accepted for publication in MNRAS