From giant planet to brown dwarf: evidence for deuterium burning in old age?

The radii of transiting giant planets and brown dwarfs have posed a critical question, as many of these objects exhibit an unexpected inflation. BD-14 3065b, a recently discovered transiting planet/brown dwarf in a triple-star system, is of particular interest due to its mass being close to the deuterium burning boundary and its surprisingly large radius. Among several potential processes that could be responsible for the inflated radius, deuterium burning appears to be a plausible explanation, resulting from the heating of BD-14 3065b’s interior. While objects within the mass range of 0.3 to 80 Jupiter masses follow a consistent trend in the mass-radius diagram, it is worthwhile to investigate whether objects above and below the 13 Jupiter masses threshold (the typical threshold distinguishing planets and brown dwarfs) are distinct. Therefore, objects that straddle this boundary present an intriguing opportunity for further study.