HD 89345: a bright oscillating star hosting a transiting warm Saturn-sized planet observed by K2. Issue 4 (29th May 2018)

• Record Type: Journal Article
• Authors: Van Eylen, V; Dai, F; Mathur, S; Gandolfi, D; Albrecht, S; Fridlund, M; García, R A; Guenther, E; Hjorth, M; Justesen, A B; Livingston, J; Lund, M N; Pérez Hernández, F; Prieto-Arranz, J; Regulo, C; Bugnet, L; Everett, M E; Hirano, T; Nespral, D; Nowak, G; Palle, E; Silva Aguirre, V; Trifonov, T; Winn, J N; Barragán, O; Beck, P G; Chaplin, W J; Cochran, W D; Csizmadia, S; Deeg, H; Endl, M; Heeren, P; Grziwa, S; Hatzes, A P; Hidalgo, D; Korth, J; Mathis, S; Montañes Rodriguez, P; Narita, N; Patzold, M; Persson, C M; Rodler, F; Smith, A M S;
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 478:Issue 4(2018)
• Page Start: 4866
• Page End: 4880
• Publication Date: 2018-05-29
• Subjects: asteroseismology -- planets and satellites: composition -- planets and satellites: formation -- planets and satellites: fundamental parameters; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty1390
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We report the discovery and characterization of HD 89345b (K2-234b; EPIC 248777106b), a Saturn-sized planet orbiting a slightly evolved star. HD 89345 is a bright star ( V = 9.3 mag) observed by the K2 mission with 1 min time sampling. It exhibits solar-like oscillations. We conducted asteroseismology to determine the parameters of the star, finding the mass and radius to be $1.12^{+0.04}_{-0.01} \mathrm{ M}_\odot$ and $1.657^{+0.020}_{-0.004} \mathrm{ R}_\odot$, respectively. The star appears to have recently left the main sequence, based on the inferred age, $9.4^{+0.4}_{-1.3} \mathrm{Gyr}$, and the non-detection of mixed modes. The star hosts a 'warm Saturn' ( P = 11.8 d, R p = 6.86 ± 0.14 R⊕ ). Radial-velocity follow-up observations performed with the FIbre-fed Echelle Spectrograph, HARPS, and HARPS-N spectrographs show that the planet has a mass of 35.7 ± 3.3 M⊕ . The data also show that the planet's orbit is eccentric ( e ≈ 0.2). An investigation of the rotational splitting of the oscillation frequencies of the star yields no conclusive evidence on the stellar inclination angle. We further obtained Rossiter–McLaughlin observations, which result in a broad posterior of the stellar obliquity. The planet seems to confirm to the same patterns that have been observed for other sub-Saturns regarding planet mass and multiplicity, orbital eccentricity, and stellar metallicity.