Spectroscopic classification of PSN J20233626-2816434 as an early peculiar type Ia supernova by the Nearby Supernova Factory II

ATel #4253; Y. Copin, E. Gangler, R. Pereira, M. Rigault, G. Smadja (IPNL);  G. Aldering, D. Birchall, M. Childress, H. Fakhouri, A. Kim, J. Nordin, P. Nugent, S. Perlmutter, K. Runge, C. Saunders, N. Suzuki, R. C. Thomas (LBNL);  E. Pecontal (CRAL);  C. Buton, U. Feindt, M. Kerschhaggl, M. Kowalski (U. Bonn);  S. Benitez, W. Hillebrandt, M. Kromer, M. Sasdelli, A. Sternberg, S. Taubenberger (MPA);  D. Baugh, J. Chen, N. Chotard, C. Wu (THCA);  C. Tao (CPPM & THCA), D. Fouchez, A. Tilquin (CPPM); E. Hadjiyska, D. Rabinowitz, C. Baltay, N. Ellman, R. McKinnon, A. Effron (Yale); F. Cellier-Holzem, A. Canto, P. Antilogus, S. Bongard, R. Pain (LPNHE)
on 12 Jul 2012; 01:26 UT
Credential Certification: Alex Kim (agkim@lbl.gov)

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The Nearby Supernova Factory II (http://snfactory.lbl.gov) reports spectroscopic confirmation of PSN J20233626-2816434 (CBAT "Transient Objects Confirmation Page") obtained July 11.5, 2012 UTC with the SuperNova Integral Field Spectrograph (Aldering et al 2002, SPIE, 4836, 61) on the University of Hawaii 2.2-meter telescope. Spectra covering the range 3200-9700 A indicate that PSN J20233626-2816434 is a peculiar Type Ia supernova. Measurement of the SiII 6350 A line indicates a photospheric velocity of 12,000 km/s assuming a redshift of 0.010187 for the host galaxy, ESO 462-G016, as reported by Theureau et al 1998, A&AS, 130, 333 (via NED). Strong CII 6580 A (cf. Thomas et al 2011, ApJ, 743, 27) is detected near the photospheric velocity. Possible very weak absorption from interstellar gas in the host galaxy is detected, with EW(NaD) = 0.05 +/- 0.05 A. Such low host absorption is consistent with the presence of the SN in the outskirts of the low inclination host galaxy. The spectral features of PSN J20233626-2816434 are quite similar to those of SN2009dc around 10 days before peak brightness, but the velocity and spectral slope are more similar to SN2006gz at a similar early phase. These Type Ia supernovae were overluminous, and it has been proposed that their masses exceed the Chandrasekhar limit. At its current reported brightness of magnitude 16.3 (unfiltered) PSN J20233626-2816434 has an absolute magnitude of approximately -17.2. At a similar phase SN2009dc had reached an absolute magnitude of approximately -19.0 (Taubenberger et al 2011, MNRAS, 412, 2735) while SN2006gz had reached an absolute magnitude of approximately -18.7 (Hicken et al 2007, ApJ 669, 17). Given the evidence for little host absorption, it is possible that the phase of PSN J20233626-2816434 is much earlier than -10 days, or that it will not reach the high peak luminosities achieved by SN2009dc and SN2006gz despite its spectral similarities. Continued follow-up of this interesting object is strongly encouraged.