K2-280 b – a low density warm sub-Saturn around a mildly evolved star. Issue 4 (17th July 2020)

• Record Type: Journal Article
• Authors: 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;
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 497:Issue 4(2020)
• Page Start: 4423
• Page End: 4435
• Publication Date: 2020-07-17
• Subjects: techniques: photometric -- techniques: radial velocities -- techniques: spectroscopic -- planets and satellites: detection -- stars: individual: (EPIC 216494238, K2-280); Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa2077
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: 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⊕ and a mass of M b = 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 T eff = 5500 ± 100 K, a surface gravity of $\log \, g_{\star }$ = 4.21 ± 0.05 (cgs), and an iron abundance of [Fe/H] = ${0.33}\, {\pm }\, {0.08}$ 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.