2012CBET.3316....2C

T.-W. Chen, R. Kotak, M. Fraser, and S. J. Smartt, Queen's University, Belfast; M. Sullivan, University of Southampton; and K. Maguire, Oxford University, report that a spectrogram (range 330-975 nm; resolution about 500) of PSN J07563555+3954072 = SN 2012gy was obtained on Nov. 22.23 UT with the 4.2-m William Herschel Telescope (+ ISIS). From narrow H-alpha emission, they determine a redshift of 0.067 for 2012gy. Cross-correlation with a library of supernova spectra via the "Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) gives a best match for 2012gy with the interacting type-Ia supernova 2002ic about a week after maximum light. They measure a minimum for the Si II 615.0-nm feature of 11000 km/s.

The weak (8 x 10**-16 erg/s/A) but real feature that they attribute to H-alpha has a FWHM of about 1.4 nm, which is the same as that of the narrow night-sky lines, suggesting that H-alpha is unresolved. This is in contrast to the broader H-alpha, which was seen in the prototypical interacting type-Ia supernova 2002ic. The authors note, however, that spatially extended H-alpha emission is not visible in the two-dimensional spectrum. Finally, a double-notched feature at around 400.0 nm rest frame is consistent with a super-Chandrasekhar explosion, which would make the detection of a H-rich circumstellar medium even more peculiar.