TOI-6508 b: A massive transiting brown dwarf orbiting a low-mass star
K. Barkaoui, Daniel Sebastian, Sebastián Zúñiga-Fernández, A. H. M. J. Triaud, Benjamin V. Rackham, Adam J. Burgasser, T.W. Carmichael, M. Gillon, Christopher A. Theissen, Emma Softich, B. Rojas-Ayala, G. Srdoc, A. Soubkiou, A. Fukui, M. Timmermans, M. Stalport, A. Burdanov, D.R. Ciardi, K.A. Collins, Yasmin Davis, Fatemeh Davoudi, J. de Wit, B. -O. Demory, Sarah Deveny, G. Dransfield, Elsa Ducrot, L. Florian, Tianjun Gan, Y. Gómez Maqueo Chew, M. J. Hooton, S. B. Howell, J.M. Jenkins, Colin Littlefield, E. L. Martín, F. Murgas, Prajwal Niraula, E. Palle, P.P. Pedersen, F. J. Pozuelos, D. Queloz, G. Ricker, R.P. Schwarz, S. Seager, A. Shporer, M. G. Scott, C. Stockdale, Joshua N. Winn
Abstract
We report the discovery of a transiting brown dwarf orbiting a low-mass star, TOI-6508 b. Today, only ∼50 transiting brown dwarfs have been discovered. TOI-6508 b was first detected with data from the Transiting Exoplanet Survey Satellite ( TESS ) in Sectors 10, 37 and 63. Ground-based follow-up photometric data were collected with the SPECULOOS-South (Search for habitable Planets EClipsing ULtra-cOOl Stars) and LCOGT-1m telescopes, and RV measurements were obtained with the Near InfraRed Planet Searcher (NIRPS) spectrograph. We find that TOI-6508 b has a mass of M p = 72.5 −5.1 +7.6 M Jup and a radius of R p = 1.03 ± 0.03 R Jup . Our modeling shows that the data are consistent with an eccentric orbit of 19 day and an eccentricity of e = 0.28 −0.08 +0.09 . TOI-6508 b has a mass ratio of M BD / M ★ = 0.40, makes it the second highest mass ratio brown dwarf that transits a low-mass star. The host has a mass of M ★ = 0.174 ± 0.004 M ⊙ , a radius of R ★ = 0.205 ± 0.006 R ⊙ , an effective temperature of T eff = 2930 ± 70 K, and a metallicity of [ Fe/H ] = −0.22 ± 0.08. This makes TOI-6508 b an interesting discovery that has come to light in a region still sparsely populated.