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ATEL # 2638; Edo Berger and Ryan Chornock (Harvard)
on 25 May 2010; 23:24 UT
Distributed as an Instant Email Notice (Supernova)
Password Certification: Edo Berger (firstname.lastname@example.org)
Subjects: Infra-Red, Optical, Nova, Supernova, Transients, Variables
Referred to by ATEL #: 2640, 2642, 2648, 2658, 2660
We report the non-detection of the progenitor of the LBV outburst SN2010da in archival Magellan/Megacam images. These images were obtained during deep follow-up observations of the low-luminosity transient NGC300 OT2008-1 (Berger et al. 2009, ApJ, 699, 1850; Bond et al. 2009, ApJ, 695, L154; Thompson et al. 2009, ApJ, 705, 1364). Astrometry relative to our Gemini-south/GMOS acquisition images (ATEL 2637) using about 100 objects in common results in an rms scatter of about 37 mas. We do not detect any coincident source in either r- or i-band to a conservative limit of 24 AB mag (see image at: http://www.cfa.harvard.edu/~eberger/SN2010da_megacam.eps).
In addition, we obtained archival Spitzer observations of NGC300 in the four IRAC bands and the MIPS 24 micron band (see also ATEL 2632). Photometry of the counterpart leads to the following AB magnitudes: 18.7 (3.6 micron), 18.5 (4.5 micron), 19.0 (5.8 micron), 19.3 (8.0 micron), and >18.5 (24 micron). The IRAC colors are significantly bluer than those of the progenitors of NGC300 OT2008-1 and SN2008S. However, a comparison to our optical upper limits indicate an r-[3.6] color of >5.3 mag. The optical/IR spectral energy distribution is shown at: http://www.cfa.harvard.edu/~eberger/SN2010da_sed.ps, with a comparison to the progenitors of NGC300 OT2008-1 and SN2008S, as well as the LBV AG Car (normalized arbitrarily at 5 microns). The progenitor SED of SN2010da is clearly distinct from the red SEDs of the NGC300 OT2008-1 and SN2008S progenitors, which peak at ~15 microns. It is also significantly redder than AG Car in the optical, but provides a good match in the IRAC bands. The addition of significant extinction, with A_V>12 mag, accommodates the IRAC and optical colors. However, we note that the 24 micron flux limit is about an order of magnitude lower than expected based on the SED of AG Car (even without the additional >12 mag of extinction). This may point to cooler dust around the progenitor of SN2010da.
Finally, we note that the detection of SN2010da with the Swift/UVOT (ATEL 2633) indicates that the dust around the progenitor was destroyed by the outburst.