The lonely fate of the lowest-mass brown dwarfs

Clémence Fontanive ( Université de Montréal )

In this talk, I will present results from HST campaigns investigating the multiplicity of the coldest free-floating brown dwarfs, at the bottom end of the IMF. Our observations confirm that wide companions are extremely rare around the lowest-mass brown dwarfs in the field, continuing the trend of decreasing binary fraction with primary mass seen throughout the stellar and substellar regimes. Since wide-separation binaries are observed among younger brown dwarfs, these results suggest that such weakly-bound systems are unlikely to survive to field ages. Our findings also support the idea that if a significant population of binaries exist around low-mass old objects, it should lie below 2–3 au separations, only accessible with JWST.