Constraints on the binary Properties of mid to late T dwarfs from Hubble Space Telescope WFC3 Observations

TL;DR

This study used HST/WFC3 to observe 26 nearby mid to late T dwarfs, searching for companions and constraining the binary fraction, finding no new companions and setting upper limits consistent with prior research.

Contribution

First to use HST/WFC3 for a systematic search of companions around mid to late T dwarfs, providing new constraints on their binary fraction.

Findings

No new companions detected, consistent with previous surveys.

Upper limit on binary fraction of <16% to <25%.

Results align with prior binary distribution models.

Abstract

We used HST/WFC3 observations of a sample of 26 nearby ($\le$20 pc) mid to late T dwarfs to search for cooler companions and measure the multiplicity statistics of brown dwarfs. Tightly-separated companions were searched for using a double-PSF fitting algorithm. We also compared our detection limits based on simulations to other prior T5+ brown dwarf binary programs. No new wide or tight companions were identified, which is consistent with the number of known T5+ binary systems and the resolution limits of WFC3. We use our results to add new constraints to the binary fraction of T-type brown dwarfs. Modeling selection effects and adopting previously derived separation and mass ratio distributions, we find an upper limit total binary fraction of <16% and <25% assuming power law and flat mass ratio distributions respectively, which are consistent with previous results. We also characterize a handful of targets around the L/T transition.