Two Intermediate-mass Transiting Brown Dwarfs from the TESS Mission
Henning, Thomas; Hellier, Coel; Latham, David W.; Quinn, Samuel N.; Jordán, Andrés; Espinoza, Néstor; Brahm, Rafael; Stassun, Keivan G.; Zhou, George; Ziegler, Carl; Collins, Karen A.; Žerjal, Maruša; Shporer, Avi; Collins, Kevin I.; Fridlund, Malcolm; Persson, Carina M.; Mann, Andrew W.; Rodriguez, Joseph E.; Ireland, Michael; Nielsen, Louise D.; Pepe, Francesco; Sarkis, Paula; Huang, Chelsea; Law, Nicholas; Briceño, César; Udry, Stephane; Bouchy, Francois; Carmichael, Theron W.; Mustill, Alexander J.; Seidel, Julia V.; Stalport, Manu
France, United States, Sweden, Switzerland, Canada, Chile, Netherlands, United Kingdom, Australia, Germany
Abstract
We report the discovery of two intermediate-mass transiting brown dwarfs (BDs), TOI-569b and TOI-1406b, from NASA's Transiting Exoplanet Survey Satellite mission. TOI-569b has an orbital period of P = 6.55604 ± 0.00016 days, a mass of Mb = 64.1 ± 1.9 ${M}_{{\rm{J}}}$ , and a radius of Rb = 0.75 ± 0.02 ${R}_{{\rm{J}}}$ . Its host star, TOI-569, has a mass of M⋆ = 1.21 ± 0.05 $\,{M}_{\odot }$ , a radius of R⋆ = 1.47 ± 0.03 $\,{R}_{\odot }$ , $[\mathrm{Fe}/{\rm{H}}]=+0.29\pm 0.09$ dex, and an effective temperature of Teff = 5768 ± 110 K. TOI-1406b has an orbital period of P = 10.57415 ± 0.00063 days, a mass of Mb = 46.0 ± 2.7 ${M}_{{\rm{J}}}$ , and a radius of Rb = 0.86 ± 0.03 ${R}_{{\rm{J}}}$ . The host star for this BD has a mass of M⋆ = 1.18 ± 0.09 $\,{M}_{\odot }$ , a radius of R⋆ = 1.35 ± 0.03 $\,{R}_{\odot }$ , $[\mathrm{Fe}/{\rm{H}}]=-0.08\pm 0.09$ dex, and an effective temperature of Teff = 6290 ± 100 K. Both BDs are in circular orbits around their host stars and are older than 3 Gyr based on stellar isochrone models of the stars. TOI-569 is one of two slightly evolved stars known to host a transiting BD (the other being KOI-415). TOI-1406b is one of three known transiting BDs to occupy the mass range of 40-50 ${M}_{{\rm{J}}}$ and one of two to have a circular orbit at a period near 10 days (with the first being KOI-205b). Both BDs have reliable ages from stellar isochrones, in addition to their well-constrained masses and radii, making them particularly valuable as tests for substellar isochrones in the BD mass-radius diagram.