K2-280 b - a low density warm sub-Saturn around a mildly evolved star
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 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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2020
- DOI:
- 10.1093/mnras/staa2077
- arXiv:
- arXiv:2007.07939
- Bibcode:
- 2020MNRAS.497.4423N
- Keywords:
-
- techniques: photometric;
- techniques: radial velocities;
- techniques: spectroscopic;
- planets and satellites: detection;
- stars: individual: (EPIC 216494238;
- K2-280);
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 14 pages, 9 figures, 5 tables, accepted for publication in MNRAS