Publication details

K2-280 b - a low density warm sub-Saturn around a mildly evolved star

Authors	NOWAK Grzegorz PALLE Enric GANDOLFI Davide DEEG Hans J. HIRANO Teruyuki BARRAGAN Oscar KUZUHARA Masayuki DAI Fei LUQUE Rafael PERSSON Carina M. FRIDLUND Malcolm JOHNSON Marshall C. KORTH Judith LIVINGSTON John H. GRZIWA Sascha MATHUR Savita HATZES Artie P. PRIETO-ARRANZ Jorge NESPRAL David HIDALGO Diego HJORTH Maria ALBRECHT Simon VAN EYLEN Vincent LAM Kristine W. F. COCHRAN William D. ESPOSITO Massimiliano CSIZMADIA Szilard GUENTHER Eike W. KABATH Petr BLAY Pere BRAHM Rafael JORDAN Andres ESPINOZA Nestor ROJAS Felipe CASASAYAS BARRIS Nuria RODLER Florian ALONSO SOBRINO Roi CABRERA Juan CARLEO Ilaria CHAUSHEV Alexander DE LEON Jerome EIGMULLER Philipp ENDL Michael ERIKSON Anders FUKUI Akihiko GEORGIEVA Iskra GONZALEZ-CUESTA Lucia KNUDSTRUP Emil LUND Mikkel N. RODRIGUEZ Pilar Montanes MURGAS Felipe NARITA Norio NIRAULA Prajwal PATZOLD Martin RAUER Heike REDFIELD Seth RIBAS Ignasi SKARKA Marek SMITH Alexis M. S. SUBJAK Jano
Year of publication	2020
Type	Article in Periodical
Magazine / Source	Monthly Notices of the Royal Astronomical Society
MU Faculty or unit	Faculty of Science
Citation
web	https://doi.org/10.1093/mnras/staa2077
Doi	http://dx.doi.org/10.1093/mnras/staa2077
Keywords	techniques: photometric; techniques: radial velocities; techniques: spectroscopic; planets and satellites: detection; stars: individual: (EPIC 216494238; K2-280)
Description	We present an independent discovery and detailed characterization of K2-280 b, a transiting low density warm sub-Saturn in a 19.9-d 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 K2-280 b has a radius of R-b = 7.50 +/- 0.44 R-circle plus and a mass of M-b = 37.1 +/- 5.6 M-circle plus, yielding a mean density of rho(b) = 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(star) = 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-circle dot and a radius of R-star = 1.28 +/- 0.07 R-circle dot. We discuss the importance of K2-280 b 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.