Spitzer Space Telescope - General Observer Proposal #50667


Effective temperatures of the Three Coolest Brown Dwarfs.

Principal Investigator: Loic Albert
           Institution: Canada-France-Hawaii Telescope

     Technical Contact: Daniel Devost, Cornell University

Co-Investigators: 
Xavier Delfosse, Grenoble University                                  
Daniel Devost, Canada-France-Hawaii Telescope                         
Philippe Delorme, Grenoble University                                 
Etienne Artigau, Gemini Observatory                                   
Thierry Forveille, Universite de Grenoble.                            
Celine Reyle, Besancon                                                
Thomas Roellig, NASA Ames                                             
Sandy Leggett, Gemini Observatory                                     
France Allard, Centre de Recherche Astronomique de Lyon               

Science Category: brown dwarfs/very low mass stars 
 Observing Modes: IracMap IrsStare 
  Hours Approved: 16.3 

Abstract:
We propose to observe three ultra cool brown dwarfs with the IRS and IRAC that
were found in the Canada-France Brown Dwarfs Survey. They were drawn from
analysis of 550 square degrees of our ongoing survey from an initial pool of 920
i'-z' <= 1.7 red objects. The three brown dwarfs we propose to observe have a
color z'-J as red or redder than the coolest known dwarf, ULAS0034, and a
similar or brighter J-band magnitude. One of our candidates, CFBDS1, is already
confirmed to be of spectral type T8.5+, and is slightly cooler than ULAS0034
(paper to be submitted). IRAC photometry combined to already available izYJHK
data is an invaluable tool to reconstuct the SED and accurately determine the
effective temperatures of these dwarfs. The IRS spectrum between 7 and 14
microns in turn will probe a temperature regime yet unexplored and constraint
the currently uncertain atmosphere models. IRAC and IRS measurements of ULAS0034
and the 3 BDs we propose to observe here will provide unique templates to
understand the many cooler dwarfs which will be discovered after the Spitzer
coolant is depleted.