TOI-6508b: A massive transiting brown dwarf orbiting a low-mass star

K. Barkaoui; D. Sebastian; S. Zúñiga-Fernández; A. H. M. J. Triaud; B. V. Rackham; A. J. Burgasser; T. W. Carmichael; M. Gillon; C. Theissen; E. Softich; B. Rojas-Ayala; G. Srdoc; A. Soubkiou; A. Fukui; M. Timmermans; M. Stalport; A. Burdanov; D. R. Ciardi; K. A. Collins; Y. T. Davis; F. Davoudi; J. de Wit; B. O. Demory; S. Deveny; G. Dransfield; E. Ducrot; L. Florian; T. Gan; Y. Gómez Maqueo Chew; M. J. Hooton; S. B. Howell; J. M. Jenkins; C. Littlefield; E. L. Martín; F. Murgas; P. 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; J. Winn

arXiv · 2502.19940

TOI-6508b: A massive transiting brown dwarf orbiting a low-mass star

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Abstract

We report the discovery of a transiting brown dwarf orbiting a low-mass star, TOI-6508b. Today, only ~50 transiting brown dwarfs have been discovered. TOI-6508b 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 and LCOGT-1.0m telescopes, and RV measurements were obtained with the Near InfraRed Planet Searcher (NIRPS) spectrograph. We find that TOI-6508b has a mass of Mp=72.5+7.6-5.1MJup and a radius of Rp=1.03+/-0.03RJup. Our modeling shows that the data are consistent with an eccentric orbit of 19day and an eccentricity of e=0.28+0.09-0.08. TOI-6508b has a mass ratio of M_BD/Ms=0.40, makes it the second highest mass ratio brown dwarf that transits a low-mass star. The host has a mass of Ms=0.174+/-0.004M_Sun, a radius of Rs=0.205+/-0.006R_Sun, an effective temperature of Teff=2930+/-70K, and a metallicity of [Fe/H]=-0.22+/-0.08. This makes TOI-6508b an interesting discovery that has come to light in a region still sparsely populated.

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K. Barkaoui, D. Sebastian, S. Zúñiga-Fernández, A. H. M. J. Triaud, B. V. Rackham, A. J. Burgasser, T. W. Carmichael, M. Gillon, C. Theissen, E. Softich, B. Rojas-Ayala, G. Srdoc, A. Soubkiou, A. Fukui, M. Timmermans, M. Stalport, A. Burdanov, D. R. Ciardi, K. A. Collins, Y. T. Davis, F. Davoudi, J. de Wit, B. O. Demory, S. Deveny, G. Dransfield, E. Ducrot, L. Florian, T. Gan, Y. Gómez Maqueo Chew, M. J. Hooton, S. B. Howell, J. M. Jenkins, C. Littlefield, E. L. Martín, F. Murgas, P. 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, J. Winn. 2025-02-27. TOI-6508b: A massive transiting brown dwarf orbiting a low-mass star. https://arxiv.org/abs/2502.19940

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