2010CBET.2252....1T

M. Turatto, Istituto Nazionale di Astrofisica (INAF), Osservatorio Astronomico di Catania; and S. Benetti, E. Cappellaro, and F. Bufano, INAF, Osservatorio Astronomico di Padova, on behalf of a larger collaboration, report that a spectrogram (range 350-1000 nm, resolution 1.4 nm) of 2010bo (cf. CBET 2238), obtained on April 18.31 UT with the New Technology Telescope (+ EFOSC2), shows it to be a type-II supernova caught after maximum; assuming a recession velocity of about 5900 km/s (as measured from the broad H_alpha component), comparison of the observed spectrum with a library of supernova spectra via the "GELATO" code (Harutyunyan et al. 2008, A.Ap. 488, 383, available at https://gelato.tng.iac.es/login.cgi) shows strong resemblance to SN 1993J at 16 days after maximum (Barbon et al. 1995, A.Ap. Suppl. 110, 513) – but for the broad H_alpha absorption feature consisting of two well-separated minima measured at 631.0 and 648.0 nm, respectively. Also, a spectrogram of 2010bt (cf. CBET 2250), obtained as above on April 18.39 UT, is that of a type-IIn supernova. The comparison of this spectrum with GELATO shows strong resemblance to several type-IIn supernovae a few days after explosion. A broad H_alpha component is also present, from which an expansion velocity of about 4500 km/s is derived.