학술논문
TOI-544 b: a potential water-world inside the radius valley in a two-planet system
Document Type
Working Paper
Author
Osborne, H. L. M.; Van Eylen, V.; Goffo, E.; Gandolfi, D.; Nowak, G.; Persson, C. M.; Livingston, J.; Weeks, A.; Pallé, E.; Luque, R.; Hellier, C.; Carleo, I.; Redfield, S.; Hirano, T.; Gili, M. Garbaccio; Alarcon, J.; Barragán, O.; Casasayas-Barris, N.; Díaz, M. R.; Esposito, M.; Jenkins, J. S.; Knudstrup, E.; 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.; Korth, J.; Lam, K. W. F.
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Abstract
We report on the precise radial velocity follow-up of TOI-544 (HD 290498), a bright K star (V=10.8), which hosts a small transiting planet recently discovered by the Transiting Exoplanet Survey Satellite (TESS). We collected 122 high-resolution HARPS and HARPS-N spectra to spectroscopically confirm the transiting planet and measure its mass. The nearly 3-year baseline of our follow-up allowed us to unveil the presence of an additional, non-transiting, longer-period companion planet. We derived a radius and mass for the inner planet, TOI-544b, of 2.018 $\pm$ 0.076 R$_{\oplus}$ and 2.89 $\pm$ 0.48 M$_{\oplus}$ respectively, which gives a bulk density of $1.93^{+0.30}_{-0.25}$ g cm$^{-3}$. TOI-544c has a minimum mass of 21.5 $\pm$ 2.0 M$_{\oplus}$ and orbital period of 50.1 $\pm$ 0.2 days. The low density of planet-b implies that it has either an Earth-like rocky core with a hydrogen atmosphere, or a composition which harbours a significant fraction of water. The composition interpretation is degenerate depending on the specific choice of planet interior models used. Additionally, TOI-544b has an orbital period of 1.55 days and equilibrium temperature of 999 $\pm$ 14 K, placing it within the predicted location of the radius valley, where few planets are expected. TOI-544b is a top target for future atmospheric observations, for example with JWST, which would enable better constraints of the planet composition.
Comment: Accepted in MNRAS, 06 December 2023
Comment: Accepted in MNRAS, 06 December 2023