Spitzer Space Telescope - Directors Discretionary Time Proposal #70203


Confirmation of a Candidate for the Coolest Known Brown Dwarf

Principal Investigator: Kevin Luhman
           Institution: Penn State University

     Technical Contact: Kevin Luhman, PSU

Co-Investigators: 
Addam Burgasser, UC San Diego
John  Bochanski, Penn State University

Science Category: brown dwarfs/very low mass stars
 Observing Modes: IRAC Post-Cryo Mapping
  Hours Approved: 0.4

Abstract:
We have used multi-epoch Spitzer/IRAC images to search for substellar 
companions to several hundred nearby stars based on their common proper 
motions. Through this work, we have identified a very promising 
candidate that could be the coldest and faintest known brown dwarf by 
a fairly large margin, and thus may inhabit a new spectral class 
(tentatively dubbed the Y class). Given the low value of our mass 
estimate (10-15 M_Jup), this object could also be a giant planet that 
formed in a disk and was scattered to a larger orbit. To verify the cool 
nature of this candidate, we propose to obtain photometry at 3.6um and 
combine it with the existing data at 4.5um to measure the 3.6-4.5um color, 
which should be very red if methane absorption is present at 3.6um. 
If confirmed as the coolest known brown dwarf, this companion will 
represent a valuable laboratory for studying atmospheres in a new 
temperature regime, and its colors will help to guide searches for 
the coolest brown dwarfs with facilities like WISE.