TOI-544 b: a potential water-world inside the radius valley in a two-planet system

DOI: 
10.1093/mnras/stad3837
Publication date: 
05/01/2024
Main author: 
Osborne, H.L.M.
IAA authors: 
Jenkins, J. S.
Authors: 
Osborne, H.L.M.; Van Eylen, V.; Goffo, E.; Gandolfi, D.; Nowak, G.; Persson, C.M.; Livingston, J.; Weeks, A.; Palle, E.; Luque, R.; Hellier, C.; Carleo, I.; Redfield, S.; Hirano, T.; Gili, M.G.; Alarcon, J.; Barragan, O.; Casasayas-Barris, N.; Díaz, M.R.; Esposito, M.; Knudstrup, E.; Jenkins, J.S.; Murgas, F.; Orell-Miquel, J.; Rodler, F.; Serrano, L.; Stangret, M.; Albrecht, S.H.; Alqasim, A.; Cochran, W.D.; Deeg, H.J.; Fridlund, M.; Hatzes, A.P.; Korth, J.; Lam, K.W.F.
Journal: 
Monthly Notices of the Royal Astronomical Society
Publication type: 
Article
Volume: 
527
Pages: 
11138–11157
Issue: 
4
Abstract: 
We report on the precise radial velocity follow-up of TOI-544 (HD 290498),ã bright K star ( V = 10.8), which hostsã small transiting planet recently disco v ered by the Trãnsiting Exoplanet Survey Satellite (TESS) . We collected 122 high-resolution High Accuracy Radial velocity Planet Searcher (HARPS)ãnd HARPS-N spectra to spectroscopically confirm the transiting planetãnd measure its mass. The nearly 3-yr baseline of our follow-upãllowed us to unveil the presence ofãnãdditional, non-transiting, longer-period companion planet. We derivedã radiusãnd mass for the inner planet, TOI-544 b, of 2.018 ±0.076 R⊙and 2.89 ±0.48 M⊙, respectively, which givesã bulk density of 1 . 93 + 0 . 30 -0 . 25 g cm -3 . TOI-544 c hasã minimum mass of 21.5 ±2.0 M⊙and orbital period of 50.1 ±0.2 d. The low density of planet-b implies that it has eitherãn Earth-like rocky core withã hydrogenãtmosphere, orã composition which harboursã significant fraction of water. The composition interpretation is degenerate depending on the specific choice of planet interior models used. Additionally, TOI-544 b hasãn orbital period of 1.55 dãnd equilibrium temperature of 999 ±14 K, placing it within the predicted location of the radius valley, where few planetsãre expected. TOI-544 b isã top target for futureãtmospheric observations, for example with JWST , which would enable better constraints of the planet composition. © 2023 The Author(s).
Database: 
SCOPUS
URL: 
https://www.scopus.com/inward/record.uri?eid=2-s2.0-85183445867&doi=10.1093%2fmnras%2fstad3837&partnerID=40&md5=35fd54c3250a7c4d657963ab4ef5c534
ADS Bibcode: 
2024MNRAS.52711138O
Keywords: 
planets and satellites: composition; planetsãnd satellites: detection; techniques: radial velocities