Sara Lindgren, Emily Martin

Sara Lindgren: Looking for companions to the coldest brown dwarfs using HST Abstract: Brown dwarfs populate an interesting parameter space between stars and planets. They have insufficient mass to sustain hydrogen fusion in their cores and, as a result, get cooler and fainter over time. Characterizing coeval companions provide unique opportunities to test brown dwarf cooling and atmospheric models, and furthermore give insight on the formation mechanism for very low-mass stars and substellar objects. High-resolution imaging of already confirmed brown dwarfs is the most successful technique to discover new binaries. However, there are still only a handful known binaries among the coldest brown dwarfs (T8 and later). In this talk I will present the results from our analysis of HST/WFC3 data of thirteen brown dwarfs, and discuss our efforts to look for very close-in, faint companions by modelling the PSFs of the brown dwarfs using the Tiny TIM software package. *********************** Emily Martin: Finding the Coldest, Closest Brown Dwarfs: Parallaxes for late-T and Y dwarfs in the Spitzer Parallax Program I will present preliminary results from the Spitzer Parallax Program, which uses Spitzer follow-up of WISE-discovered brown dwarfs to perform astrometric monitoring of the coldest and faintest brown dwarfs. These objects cannot be easily observed from the ground. We are measuring parallaxes for a volume-limited sample of late-type T and Y dwarfs in order to complete the census of ultra-cool dwarfs in the solar neighborhood. I will discuss our progress to date, including distance measurements for 22 late-T and Y dwarfs in our sample and spectroscopic confirmation of 3 late-T dwarfs.