We report the discovery of a warm sub-Saturn, TOI-257b (HD 19916b), based on data from NASA's Transiting Exoplanet Survey Satellite (TESS). The transit signal was detected by TESS and confirmed to be of planetary origin based on radial velocity observations. An analysis of the TESS photometry, the MINERVA-Australis, FEROS, and HARPS radial velocities, and the asteroseismic data of the stellar oscillations reveals that TOI-257b has a mass of MP = 0.138 ± 0.023 MJ (43.9 ± 7.3 M⊕ ), a radius of RP = 0.639 ± 0.013 RJ (7.16 ± 0.15 R⊕ ), bulk density of 0.65+0.12−0.11 (cgs), and period 18.38818+0.00085−0.00084 days . TOI-257b orbits a bright (V = 7.612 mag) somewhat evolved late F-type star with M* = 1.390 ± 0.046 Msun , R* = 1.888 ± 0.033 Rsun , Teff = 6075 ± 90 K , and vsin i = 11.3 ± 0.5 km s-1. Additionally, we find hints for a second non-transiting sub-Saturn mass planet on a ∼71 day orbit using the radial velocity data. This system joins the ranks of a small number of exoplanet host stars (∼100) that have been characterized with asteroseismology. Warm sub-Saturns are rare in the known sample of exoplanets, and thus the discovery of TOI-257b is important in the context of future work studying the formation and migration history of similar planetary systems.
SEEK ID: https://publications.h-its.org/publications/1365
Research Groups: Theory and Observations of Stars
Publication type: Journal
Journal: Monthly Notices of the Royal Astronomical Society
Citation: Monthly Notices of the Royal Astronomical Society 502(3):3704-3722
Date Published: 1st Apr 2021
Registered Mode: by DOI
Views: 4089
Created: 9th Dec 2021 at 13:29
Last updated: 5th Mar 2024 at 21:24
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