K2-140b and K2-180b – Characterization of a hot Jupiter and a mini-Neptune from the K2 mission. Issue 2 (12th October 2018)

• Record Type: Journal Article
• Authors: Korth, J; Csizmadia, Sz; Gandolfi, D; Fridlund, M; Pätzold, M; Hirano, T; Livingston, J; Persson, C M; Deeg, H J; Justesen, A B; Barragán, O; Grziwa, S; Endl, M; Tronsgaard, R; Dai, F; Cochran, W D; Albrecht, S; Alonso, R; Cabrera, J; Cauley, P W; Cusano, F; Eigmüller, Ph; Erikson, A; Esposito, M; Guenther, E W; Hatzes, A P; Hidalgo, D; Kuzuhara, M; Montañes, P; Napolitano, N R; Narita, N; Niraula, P; Nespral, D; Nowak, G; Palle, E; Petrillo, C E; Redfield, S; Prieto-Arranz, J; Rauer, H; Smith, A M S; Tortora, C; Van Eylen, V; Winn, J N;
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 482:Issue 2(2019)
• Page Start: 1807
• Page End: 1823
• Publication Date: 2018-10-12
• Subjects: techniques: photometric -- techniques: radial velocities -- stars: individual: K2-140 -- stars: individual: K2-180 -- planets and satellites: fundamental parameters -- stars: fundamental parameters; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty2760
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We report the independent discovery and characterization of two K2 planets: K2-180b, a mini-Neptune-sized planet in an 8.9-d orbit transiting a V = 12.6 mag, metal-poor ([Fe/H] = −0.65 ± 0.10) K2V star in K2 campaign 5; K2-140b, a transiting hot Jupiter in a 6.6-d orbit around a V = 12.6 mag G6V ([Fe/H] = + 0.10 ± 0.10) star in K2 campaign 10. Our results are based on K2 time-series photometry combined with high-spatial resolution imaging and high-precision radial velocity measurements. We present the first mass measurement of K2-180b. K2-180b has a mass of M p = 11.3 ± 1.9 $\mathrm{M_{{\oplus }}}$ and a radius of R p = 2.2 ± 0.1 $\mathrm{R_{{\oplus}}}$, yielding a mean density of ρp = 5.6 ± 1.9 g cm −3, suggesting a rocky composition. Given its radius, K2-180b is above the region of the so-called 'planetary radius gap'. K2-180b is in addition not only one of the densest mini-Neptune-sized planets, but also one of the few mini-Neptune-sized planets known to transit a metal-poor star. We also constrain the planetary and orbital parameters of K2-140b and show that, given the currently available Doppler measurements, the eccentricity is consistent with zero, contrary to the results of a previous study.