Spitzer Space Telescope - General Observer Proposal #50367


Precision Tests of Ultracool Dwarf Atmospheric Models

Principal Investigator: Michael  Cushing
           Institution: University of Arizona

     Technical Contact: Michael  Cushing, University of Arizona

Co-Investigators: 
Michael Liu, IfA, University of Hawaii                                
Didier Saumon, Los Alamos National Laboratory                         
Mark Marley, NASA Ames                                                
Trent Dupuy, IfA, University of Hawaii                                

Science Category: brown dwarfs/very low mass stars 
 Observing Modes: IracMap IrsStare 
  Hours Approved: 20.7 

Abstract:
Theoretical models of ultracool atmospheres are fundamental tools for
understanding and characterizing brown dwarfs and extrasolar planets. However,
current tests of these models are impeded by the heterogenous nature of field L
and T dwarfs. We propose to circumvent this limitation by studying a careful
chosen set of ultracool dwarfs with independently determined ages and/or masses.
These "benchmark" objects can provide the most stringent tests currently
possible for atmospheric models, a factor of ~5 more precise than typical field
objects. With our proposed IRS Short-Low spectroscopy and IRAC photometry, in
combination with existing optical/near-IR spectroscopy, we will construct high
S/N 0.9-14.5 SEDs and compare to state-of-the-art theoretical atmospheric
models. The mid-IR provides essential information about several fundamental
spectral diagnostics (CO, H2O, CH4, and NH3) and the overall emergent flux.
Thus, our proposed Spitzer observations are critical to testing and thereby
improving the models. Without these data, such precise tests of ultracool
atmospheres will not be possible until the availability of JWST.