Spitzer Space Telescope - Directors Discretionary Time Proposal #229


Dust around the Planet-bearing M Star Gliese 436

Principal Investigator: Charles Beichman
           Institution: JPL

Co-Investigators: 
K. Grogan, JPL                                                        
E. Holmes, JPL                                                        
T. Velusamy, JPL                                                      
M. Shao, JPL                                                          
K. Staplfeldt, JPL                                                    
J. Lunine, U. of Arizona                                              
G. Rieke, U. of Arizona                                               
G. Marcy, UC Berkeley                                                 
D. Fischer, UC Berkeley                                               
J. Greaves, ROE                                                       
W. Holland, ROE                                                       
M. Wyatt, ROE                                                         
W. Dent, ROE                                                          

Science Category: circumstellar/debris disks 
 Observing Modes: IrsStare MipsPhot 
  Hours Approved: 1.3 

Abstract:
As Spitzer investigators with a direct interest in the search for
debris disks around stars with planets based on our approved GO-1
program on Comparative Planetology, we would like to request 1.3 hr of
Director's Discretionary time to observe Gliese 436.  This M2.5 star
is located just 10  pc away, and, as was just announced (Marcey et al.
2004), has a Uranus/Neptune mass planet orbiting it with a 3 day
period.  GJ436 will quickly become a critical star for future planet
searches.  Because of its proximity and low stellar mass, an
Earth-mass planet orbiting GJ436 at 1 AU would be detectable by SIM.
Spitzer will detect or set strong limits on a dust cloud (Kuiper or
asteroid belt) associated with this star/planet system.  Since the
similarly nearby M star AU Mic has recently been found to have a
prominent disk using coronagraphy (and Spitzer observations are
planned), it would be of great interest to determine whether GJ436,
only the second M star known to have a planet, also has an associated
debris disk.  Spitzer GTO data show that between 10-25% of mature
(>3Gyr) F5-K5 stars with planets have prominent excesses at 70um
(Beichman et al, in prep 2004), so there is a reasonable prospect of
success even if this star is old.  GJ436 is not in any GO or GTO
program that we can identify.