Isobel (preliminary): Definitely a supernova. Either z~0.35 or z~0.56, I think probably the latter.
The best match (by eye) that I could get from the templates I have is 90N at -14 days. Perhaps someone else could have a look at this since we may have caught it nice and early.
Andy (preliminary): Actually, I would guess that S02-064 is past maximum. It may even be a Ib/c -- it looks a lot like SN 1994I at +11d at z=0.33 (this is my best fit, albeit after subtracting an E galaxy, which is inconsistent with a Ib/c SN). I interpret the comments in SN Trak to mean that there is light in the reference, so that is a possibility.
I don't like any of the fits past 8500 A, but these jumped around between the two data reductions. To me the SN looks past maximum because of the relative narrowness of the features.
Note that Lifan's fit above is to an older data reduction, but he gets SN 1990N at -7d at z=0.57 as the best fit. His program is evidently fitting to a peak at 5500 A which is not there in the newer data reduction.
Lifan (preliminary): I made a fit with the new data and still think 0.56 to be the best redshift. A Ic at 0.33 11 days past max is highly unlikely as Ic at that phase are too red to fit the observed.
Andy (preliminary): I disagree, see this figure, which is an overplot of the S02-064 spectrum and the dereddened SN 1994I +11d spectrum. The colors are the same.
Lifan (preliminary): I guess the the difference is that we are applying different extinction corrections to 94I which is quite uncertain and is even somewhat arbitrary - with published values from Av=3.1 to 1.0. Now that Rob has provided a phase estimate it seems more likely that this can actually be a Ia at z = 0.34. In my X2 plot, pre-max fits favors z = 0.56, post-max favors 0.3+.
Rob: Another look at S02-064, and I realize that the lightcurve is dropping *awfully* fast... we're talking stretch 0.5 fast if it really is at z=0.56.
What other sorts of things does the spectrum suggest that this candidate might be? Are there Ic's with fast-dropping lightcurves?
Andy:Oh yes. SN 1994I (the one that I fit) had delta m_15(B) = 2.1. In other words, it had a higher delta m15, or lower stretch than any Type Ia. But be aware that SN 1994I was only a good match at z=0.33. Can you try a fit at z=0.33?
Rob:Similar results. It's a very ugly fit, mind you-- but I'm fitting a Ia template and using Ia K-corrections, so it's not clear how meaningful it is.
*If* it's at z=0.33, and *if* the differential K-corrections between day 0 and day 15 are small, and *if* it was at max at discovery, and *if* the relative color term between SuPrimeCam and WIYN are small, and *if* the supernova hadn't exploded yet during the apr9 reference run then we've got a delta-m-7 (may9-may18) of 1.7. Which is huge. But that's a whole lotta ifs.
One caution on all of this: I haven't applied color terms, which *will* be reasonably significant; I'm using a Subaru reference for other telescopes, which isn't quite the right thing to do.