2010CBET.2323....1S

J. M. Silverman, S. B. Cenko, D. Poznanski, and A. V. Filippenko, University of California, Berkeley, report that inspection of CCD spectra (range 350-1000 nm), obtained on June 12 UT with the 10-m Keck I telescope (+ LRIS), shows that 2010cs (CBET 2284) is a type-Ia supernova. Cross- correlation with a library of supernova spectra using the "SuperNova IDentification" code of Blondin and Tonry (2007, Ap.J. 666, 1024) indicates that 2010cs is about one month past maximum brightness. SN 2010ct (CBET 2285) is a type-II supernova, probably of the IIP subtype and roughly one month after the explosion; H-alpha exhibits a well-developed P-Cyg profile; after removal of the host-galaxy recession velocity of 8300 km/s, determined from narrow emission features, the absorption minimum of the H-alpha line is found to be blueshifted by about 6400 km/s. SN 2010du (CBET 2308) is also a type-II supernova, probably a type-IIP event roughly one month after the explosion; its spectrum is very similar to that of SN 2010ct. A CCD spectrum obtained in bright twilight, and only over the wavelength range 350-560 nm, indicates that 2010eb (CBET 2321) is a supernova, probably of type Ia and more than 1 month past maximum brightness.