EPIC 212036875b griz light curves

EPIC 212036875b is a rare object that resides in the brown dwarf desert. In the mass-density diagram for planets, brown dwarfs and stars, we find that all giant planets and brown dwarfs follow the same trend from 0.3M_J_ to the turn-over to hydrogen burning stars at 73M_J_. EPIC 212036875b falls on the theoretical line for H/He dominated planets in this diagram as determined by interior structure models, as well as on the empirical fit.

We argue that EPIC 212036875b formed via gravitational disc instabilities in the outer part of the disc, followed by a quick migration. Orbital tidal circularisation may have started early in its history for a brief period when the brown dwarf's radius was larger. The lack of spin-orbit synchronisation points to a weak stellar dissipation parameter which implies a circularisation timescale of 23Gyr, or suggests an interaction between the magnetic and tidal forces of the star and the brown dwarf.