2012CBET.3054....4S

A. Siviero, L. Tomasella, A. Pastorello, S. Benetti, and U. Munari, Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Padova; M. Ergon, J. Sollerman, and F. Taddia, Department of Astronomy, Stockholm University; and G. Barisevicius, Nordic Optical Telescope, report that two spectra of PSN J10435372+1140177 = SN 2012aw were obtained on Mar. 19.85 UT with the 1.22-m Galileo telescope (+ Boller & Chivens spectrograph; range 320-780 nm, resolution 0.7 nm) and on Mar. 19.92 with the 2.5-m Nordic Optical Telescope (+ ALFOSC; range 320-910 nm, resolution 1.6 nm). They suggest that the object is a very young type-II supernova. Cross-correlation with a library of supernova spectra via GELATO (Harutyuyan et al. 2008, A.Ap. 488, 383) gives an excellent fit with the type-IIP supernova 1999gi (Leonard et al. 2002, A.J. 124, 2490) about 4-5 days after the core-collapse. The spectra of 2012aw show a very blue continuum and very prominent, broad hydrogen and He I 587.6-nm lines with a P-Cyg profile. The ejecta velocity, as deduced from the minimum of H_alpha, is about 15000 km/s. There is a clear evolution if these spectra are compared with that obtained on Mar. 18.77 at the 1.22-m Galileo telescope, which showed a blue, featureless continuum.