Characterizing the Sun's 4th Closest Neighbor and the Coldest Known Brown Dwarf

0 Assigned ID: 21 ----- Attempting Submission 1 (Sun Mar 30 12:53:06 GMT 2014) ----- Please check the proper motion as well as the units since the entered value exceeds the fastest object in Luyten's Half-Second Catalogue. This submission contains a new visit (#4), which is a repeat of the observations that failed in visit #3. 2138887027 ----- Attempting Submission 1 (Sat Jun 28 14:01:26 GMT 2014) ----- ----- Attempting Submission 2 (Wed Mar 11 20:55:32 GMT 2015) ----- The proper motion is correct. The target has the 3rd largest proper motion of any star in the sky. Characterizing the Sun's 4th Closest Neighbor and the Coldest Known Brown Dwarf I have conducted a search for high proper motion brown dwarfs using multi-epoch all-sky mid-infrared images from the WISE satellite. Through this work, I have discovered an object with a parallactic distance of 2.2 pc and a temperature of 250 K, making it the 4th closest neighbor of the Sun, and the coldest known brown dwarf. Because of its extreme proximity and temperature, it represents an unparallaled laboratory for studying planet-like atmospheres in an unexplored temperature regime. I propose to obtain deep near-IR images of this object in the single most sensitive band of WFC3 in order to 1) test the predicted near- to mid-IR colors of the coldest brown dwarfs, 2) assess the feasibility of more detailed observations through multi-band photometry and spectroscopy, 3) improve the accuracy of its parallax measurement, and 4) better constrain its multiplicity. This program consists of WFC3/IR images in F110W of a single faint point source during six orbits. The observations have been designed to maximize the total exposure time, optimize the spatial resolution, and provide sufficient flexibility for scheduling. The images will be obtained through three identical two-orbit visits. In each orbit, one exposure (SPARS100, NSAMP=10, 900 sec) will be collected at each position in a three-point dither pattern (WFC3-IR-DITHER-LINE-3PT). In each visit, the dither patterns in the two orbits will be offset by 3.5 pixels along the x-axis of the array. COOL STARS 12 Regular false false false false false SUPPORTED STAR BROWN DWARF J2000 J2000 WFC3/IR Imaging No No F110W POS-TARG DITHER DITHER 3 0.4725 WFC3-IR-DITHER-LINE-3PT false false 0.605 2 0 POS-TARG LINE 41.788 1

true

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