TOI-1994b: A Low-mass Eccentric Brown Dwarf Transiting A Subgiant Star

Abstract We present the discovery of TOI-1994b, a low-mass brown dwarf transiting a hot subgiant star on a moderately eccentric orbit. TOI-1994 has an effective temperature of 7700 − 410 + 720 K, V magnitude of 10.51 mag and log( g ) of 3.982 − 0.065 + 0.067 . The brown dwarf has a mass of 22.1 − 2.5 + 2.6 M J , a period of 4.034 days, an eccentricity of 0.341 − 0.059 + 0.054 , and a radius of 1.220 − 0.071 + 0.082 R J . TOI-1994b is more eccentric than other transiting brown dwarfs with similar masses and periods. The population of low-mass brown dwarfs may have properties similar to planetary systems if they were formed in the same way, but the short orbital period and high eccentricity of TOI-1994b may contrast this theory. An evolved host provides a valuable opportunity to understand the influence stellar evolution has on the substellar companion’s fundamental properties. With precise age, mass, and radius, the global analysis and characterization of TOI-1994b augments the small number of transiting brown dwarfs and allows the testing of substellar evolution models.