Spitzer Space Telescope - General Observer Proposal #80023


Constraining the Origin and Heating Mechanism of Dust in Type IIn Supernovae

Principal Investigator: Ori Fox
           Institution: NASA Goddard Space Flight Center

     Technical Contact: Ori Fox, NASA Goddard Space Flight Center

Co-Investigators: 
Michael Skrutskie, University of Virginia                             
Roger Chevalier, University of Virginia                               
Samuel Harvey Moseley, NASA Goddard Space Flight Center               

Science Category: evolved stars/pn/sne 
 Observing Modes: IRAC Post-Cryo Mapping
  Hours Approved: 9.3 

Abstract:
More than any other supernova subclass, Type IIn supernovae tend to exhibit
late-time (>100 days) infrared emission from warm dust. Identifying the origin
and heating mechanism of the dust provides an important probe of the supernova
explosion, circumstellar environment, and progenitor system. Yet mid-infrared
observations, which span the peak of the thermal emission, are rare. Two years
ago, we executed a warm Spitzer survey (P60122) of sixty-eight Type IIn events
from the past ten years. The survey uncovered nine supernovae with unreported
late-time infrared excesses, in some cases more than 5 years post-explosion.
From this single epoch of data, and ground-based optical data, we have
determined the likely origin of the mid-infrared emission to be pre-existing
dust that is continuously heated by optical emission generated by ongoing
circumstellar interaction between the forward shock and circumstellar medium.
Furthermore, we noticed an emerging trend suggests these supernovae ``turn off''
at ~1000-2000 days post-discovery once the forward shock overruns the dust
shell. Now is the ideal time to build upon this work with a second epoch of
observations, which will be necessary to constrain our models. If we catch even
a single supernova turning off between the first and second epochs of
observation, we will be able to both measure the size of the circumstellar dust
shell and characterize of the supernova progenitor system. We can obtain all the
necessary data in only 9.3 hours of observation. Our team has extensive
experience in infrared supernovae observations. We have already published two
papers on one Type IIn supernovae (SN 2005ip) and authored two successful
proposal for Spitzer observations of this subclass. This is an ideal application
for the Spitzer warm mission, as the 3.6 and 4.5 micron bands span the peak of
the thermal emission and provide the necessary constraints on the dust
temperature, mass, and luminosity.