Populating the brown dwarf and stellar boundary: Five stars with transiting companions near the hydrogen-burning mass limit
Creators: name: Grieves, Nolan
name: Bouchy, François
name: Lendl, Monika
name: Carmichael, Theron
name: Mireles, Ismael
name: Shporer, Avi
name: McLeod, Kim K.
name: Collins, Karen A.
name: Brahm, Rafael
name: Stassun, Keivan G.
name: Gill, Sam
name: Bouma, Luke G.
name: Guillot, Tristan
name: Cointepas, Marion
name: Santos, Leonardo A. Dos
name: Casewell, Sarah L.
name: Jenkins, Jon M.
name: Henning, Thomas
name: Nielsen, Louise D.
name: Psaridi, Angelica
name: Udry, Stéphane
name: Ségransan, Damien
name: Eastman, Jason D.
name: Zhou, George
name: Abe, Lyu
name: Agabi, Abelkrim
name: Charbonneau, David
name: Collins, Kevin I.
name: Colon, Knicole D.
name: Crouzet, Nicolas
name: Dransfield, Georgina
name: Evans, Phil
name: Goeke, Robert F.
name: Hart, Rhodes
name: Irwin, Jonathan M.
name: Jensen, Eric L. N.
name: Jordán, Andrés
name: Kielkopf, John F.
name: Latham, David W.
name: Marie-Sainte, Wenceslas
name: Mékarnia, Djamel
name: Nelson, Peter
name: Quinn, Samuel N.
name: Radford, Don J.
name: Rodriguez, David R.
name: Rowden, Pamela
name: Schmider, François-Xavier
name: Schwarz, Richard P.
name: Smith, Jeffrey C.
name: Stockdale, Chris
name: Suarez, Olga
name: Tan, Thiam-Guan
name: Triaud, Amaury H. M. J.
name: Waalkes, William
name: Wingham, Geof
Publisher: name: arXiv
Year: 2021
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We report the discovery of five transiting companions near the hydrogen-burning mass limit in close orbits around main sequence stars originally identified by the Transiting Exoplanet Survey Satellite (TESS) as TESS Objects of Interest (TOIs): TOI-148, TOI-587, TOI-681, TOI-746, and TOI-1213. Using TESS and ground-based photometry as well as radial velocities from the CORALIE, CHIRON, TRES, and FEROS spectrographs, we found the companions have orbital periods between 4.8 and 27.2 days, masses between 77 and 98 $\mathrm{M_{Jup}}$, and radii between 0.81 and 1.66 $\mathrm{R_{Jup}}$. These targets have masses near the uncertain lower limit of hydrogen core fusion ($\sim$73-96 $\mathrm{M_{Jup}}$), which separates brown dwarfs and low-mass stars. We constrained young ages for TOI-587 (0.2 $\pm$ 0.1 Gyr) and TOI-681 (0.17 $\pm$ 0.03 Gyr) and found them to have relatively larger radii compared to other transiting companions of a similar mass. Conversely we estimated older ages for TOI-148 and TOI-746 and found them to have relatively smaller companion radii. With an effective temperature of 9800 $\pm$ 200 K, TOI-587 is the hottest known main-sequence star to host a transiting brown dwarf or very low-mass star. We found evidence of spin-orbit synchronization for TOI-148 and TOI-746 as well as tidal circularization for TOI-148. These companions add to the population of brown dwarfs and very low-mass stars with well measured parameters ideal to test formation models of these rare objects, the origin of the brown dwarf desert, and the distinction between brown dwarfs and hydrogen-burning main sequence stars.
description: 25 pages, 14 figures, Accepted by Astronomy &amp; Astrophysics