Nowak, Grzegorz; Palle, Enric; Gandolfi, Davide; Deeg, Hans J.; Hirano, Teruyuki; Barragán, 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, Szilárd; Guenther, Eike W.; Kabath, Petr; Blay, Pere; Brahm, Rafael; Jordán, Andrés; Espinoza, Néstor; Rojas, Felipe; Casasayas Barris, Núria; Rodler, Florian; Alonso Sobrino, Roi; Cabrera, Juan; Carleo, Ilaria; Chaushev, Alexander; de Leon, Jerome; Eigmüller, Philipp; Endl, Michael; Erikson, Anders; Fukui, Akihiko; Georgieva, Iskra; González-Cuesta, Lucía; Knudstrup, Emil; Lund, Mikkel N.; Montañes Rodríguez, Pilar; Murgas, Felipe; Narita, Norio; Niraula, Prajwal; Pätzold, Martin; Rauer, Heike; Redfield, Seth; Ribas, Ignasi; Skarka, Marek; Smith, Alexis M. S.; Subjak, Jano
Bibliographical reference
Monthly Notices of the Royal Astronomical Society
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 Rb = 7.50 ± 0.44 R⊕ and a mass of Mb = 37.1 ± 5.6 M⊕, yielding a mean density of ρb = $0.48 _{ - 0.10 } ^ { + 0.13 }$ ${\rm g\, cm^{-3}}$. The host star is a mildly evolved G7 star with an effective temperature of Teff = 5500 ± 100 K, a surface gravity of $\log \, g_{\star }$ = 4.21 ± 0.05 (cgs), and an iron abundance of [Fe/H] = ${0.33}\, {\pm }\, {0.08}$ dex, and with an inferred mass of M⋆ = 1.03 ± 0.03 M☉ and a radius of R⋆ = 1.28 ± 0.07 R☉. 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.
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