Spitzer Space Telescope - General Observer Proposal #60166


Late-Time Light from Type Ia Supernovae

Principal Investigator: Peter Garnavich
           Institution: University of Notre Dame

     Technical Contact: Peter Garnavich, University of Notre Dame

Co-Investigators: 
Peter Milne, University of Arizona                                    
Ryan Foley, Center for Astrophysics                                   
Kevin Krisciunas, Texas A&M                                           
Howie Marion, Texas A&M                                               
Michael Wood-Vasey, Univ. Pittsburgh                                  
Bradley Tucker, Austrailian National Univ.                            
Thomas Matheson, NOAO                                                 

Science Category: extragalactic stellar studies 
 Observing Modes: IRAC Post-Cryo Mapping
  Hours Approved: 18.0 

Abstract:
We propose to study the physics of type Ia supernovae at late and very-late
phases of their evolution. Type Ia events produce radioactive elements that keep
the expanding debris glowing for years after the explosion. Between one and
three months after maximum, nearly all type Ia events have identical colors in
optical bands: the Lira law. This is surprising and useful as it is not
predicted by models but empirically allows dust reddening to be reliably
measured. The colors in the infrared are not as well known and we propose to
obtain multi-band light curves of three type Ia events during this "Lira law"
phase. These will be low-impact ToO observations triggered near maximum light
with observations 5 weeks later. At very late times (>200 days) the supernova
light is driven by positrons from the radioactive decay and the light curve
becomes sensitive to the magnetic environment in the debris. As the type Ia
ages, near-IR data suggest that more and more of the luminosity comes out at
long wavelengths. We propose to observe SN2008Q and another nearby supernova to
determine the fraction of bolometric luminosity coming from the mid-IR. These
observations will be supported with an extensive network of ground-based
telescopes.