Constraints on the Binary Properties of Mid- to Late T Dwarfs from Hubble Space Telescope WFC3 Observations
Mora, A.; Martín, E. L.; Solano, E.; Burgasser, A. J.; Aberasturi, M.; Reid, I. N.; Looper, D.
Spain, United States
Abstract
We used Hubble Space Telescope/Wide Field Camera 3 (WFC3) observations of a sample of 26 nearby (<=20 pc) mid- to late T dwarfs to search for cooler companions and measure the multiplicity statistics of brown dwarfs (BDs). Tightly separated companions were searched for using a double point-spread-function-fitting algorithm. We also compared our detection limits based on simulations to other prior T5+ BD 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 (BF) of T-type BDs. Modeling selection effects and adopting previously derived separation and mass ratio distributions, we find an upper limit total BF 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.
Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy Inc., under NASA contract NAS 5-26555. These observations are associated with programs 11631 and 11666.