Hubble Space Telescope WFC3 observations of L and T dwarfs.

We used HST/WFC3 observations of a sample of 35 nearby (<30 pc) late L- and T-type field brown dwarfs to examine the frequency and properties of multiple systems across the L dwarf/T dwarf transition, and search for cooler companions. The observations aim to address two of the most outstanding problems in low-temperature brown dwarf astrophysics today: the mechanism for cloud depletion across the L/T transition, and the multiplicity statistics of brown dwarfs as they relate to formation mechanisms. The targets were characterized using F110W, F127M, F139M and F164N filters, from which we derived color-spectral type calibrations to identify well-resolved companions. Tightly-separated companions were searched for using a double-PSF fitting algorithm. We also compared our detection limits based on simulations to other prior HST/WFPC2 and HST/NICMOS programs. Neither new wide or tight companions were identified. We use our results to add new constraints to the binary fraction of L/T transition systems and the Y dwarf companion rate.