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We report the discovery of five transiting companions near thehydrogen-burning mass limit in close orbits around main sequence starsoriginally identified by the Transiting Exoplanet Survey Satellite (TESS) asTESS Objects of Interest (TOIs): TOI-148, TOI-587, TOI-681, TOI-746, andTOI-1213. Using TESS and ground-based photometry as well as radial velocitiesfrom the CORALIE, CHIRON, TRES, and FEROS spectrographs, we found thecompanions have orbital periods between 4.8 and 27.2 days, masses between 77and 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 corefusion ($\sim$73-96 $\mathrm{M_{Jup}}$), which separates brown dwarfs andlow-mass stars. We constrained young ages for TOI-587 (0.2 $\pm$ 0.1 Gyr) andTOI-681 (0.17 $\pm$ 0.03 Gyr) and found them to have relatively larger radiicompared to other transiting companions of a similar mass. Conversely weestimated older ages for TOI-148 and TOI-746 and found them to have relativelysmaller companion radii. With an effective temperature of 9800 $\pm$ 200 K,TOI-587 is the hottest known main-sequence star to host a transiting browndwarf or very low-mass star. We found evidence of spin-orbit synchronizationfor TOI-148 and TOI-746 as well as tidal circularization for TOI-148. Thesecompanions add to the population of brown dwarfs and very low-mass stars withwell measured parameters ideal to test formation models of these rare objects,the origin of the brown dwarf desert, and the distinction between brown dwarfsand hydrogen-burning main sequence stars.

Populating the brown dwarf and stellar boundary: Five stars with transiting companions near the hydrogen-burning mass limit