2010CBET.2108....2C

A spectrum (range 420-1080 nm), obtained on 2010 Jan. 1.40 with the 9.2-m Hobby-Eberly Telescope (+ Marcario Low-Resolution Spectrograph) by J. Caldwell, shows a blue continuum with broad features of Si II (635 nm), Fe II (the "W" feature at 500 nm), and the Ca II infrared triplet – characteristics of a supernova of type Ic or Ia near maximum light. O I (777 nm) is absent or very weak, and all the features are broader and weaker than those in normal type-Ia supernovae. A narrow H_alpha emission from the host galaxy is also detected. The GELATO code (Harutyunyan et al. 2008, A.Ap. 488, 383; https://gelato.tng.iac.es) finds SNe 1990W (of type Ib/c, at one day after maximum) and 2004aw (type Ic, between 1 and 9 days after maximum) as the best-matching templates. On the contrary, the SuperNova IDentification code (SNID, Blondin and Tonry 2007, Ap.J. 666, 1024) classifies 2009np as a type-Ia or type-Ic supernova with 75- and 25-percent probability, respectively. Despite the result by SNID, the better match with the spectra of type-Ic supernovae and the position of 2009np within its host galaxy (very close to the apparent center) make the type-Ic classification more likely. The expansion velocity, calculated from the minimum of the Si II 635.5 nm feature, is 11000 km/s.