Spitzer Space Telescope - Directors Discretionary Time Proposal #230


Follow-up observations to the SST discovery of dust emission from SN
2002hh in NGC 6946

Principal Investigator: Michael Barlow
           Institution: University College London

Co-Investigators: 
Janet Bowey, University College London                                
Geoffrey Clayton, Louisiana State University                          
Martin Cohen, University of California, Berkeley                      
Ethan Deneault, Clemson University                                    
Joanna Fabbri, University College London                              
Tim Gledhill, University of Hertfordshire                             
Karl Gordon, Steward Observatory, University of Arizona               
Margaret Meixner, Space Telescope Science Institute                   
Nino Panagia, Space Telescope Science Institute                       
Angela Speck, University of Missouri                                  
Ben Sugerman, Space Telescope Science Institute                       
Alexander Tielens, University of Groningen                            
Douglas Welch, McMaster University                                    
Michael Wolff, Space Science Institute, University of Colorado        
Albert Zijlstra, UMIST, Manchester                                    

Science Category: evolved stars/pn/sne 
 Observing Modes: IrsStare MipsPhot 
  Hours Approved: 1.3 

Abstract:
On September 6th we reported (Barlow et al.;  IAUC 8400) the
3.6--8.0-um detection of the Type~II supernova SN 2002hh (located in
the face-on spiral galaxy NGC 6946 at a distance of 6~Mpc), in
archival Spitzer Space Telescope (SST) SINGS Legacy IRAC images taken
on June 10.76 2004, when the 8.0-um flux of the supernova was 20.0
mJy.  Since then we have also measured its flux in a SINGS Legacy MIPS
24-um image, taken one month after the IRAC data, which became
available this week.  SN 2002hh's IRAC+MIPS energy distribution can be
fit by a 300K blackbody.  Its equivalent blackbody emission radius of
1x10^17 cm is too large for the emitting dust to have been freshly
condensed in the supernova (SN) ejecta, so it appears that the dust
may have been formed and ejected in an earlier stage of evolution of
the massive progenitor star and flash heated by the SN event.
Gemini-N Director's Discretionary Time has been awarded to us this
week for high angular resolution 3-20-um observations of SN 2002hh, to
be be carried out in the next few weeks.  We have also submitted a
request for HST DD Time, with the aim of obtaining high angular
resolution observations of SN 2002hh and its surrounds at optical and
near-IR wavelengths, using the ACS and NICMOS (PI:  B.  Sugerman).
Here we request SST Director's Discretionary Time for follow-up IR
observations of the likely transient dust emission from this object.
We request that IRS spectroscopy, together with IRAC+MIPS photometry,
be obtained as early as possible (the supernova could fade to a level
several times weaker than on June 10th 2004 and still produce good
signal-to-noise ratios throughout most of the IRS spectral domain).
As well as allowing the object's overall energy distribution to be
constrained, the spectra will enable any dust emission or absorption
features to be identified (an Av of 5.0  local to the SN has been
deduced), together with any ionic emission lines.  Accompanying
short-duration IRAC 4-band and MIPS 24-um imaging will provide higher
angular resolution than the IRS