2010CBET.2223....1S

J. M. Silverman, I. K. W. Kleiser, A. J. L. Morton, and A. V. Filippenko, University of California, Berkeley, report that inspection of CCD spectra (range 340-1000 nm), obtained on Mar. 22 UT with the 3-m Shane reflector (+ Kast) at Lick Observatory, shows that SN 2010an (CBET 2211) is a moderately reddened, normal type-Ia supernova; after removal of the host-galaxy recession velocity of 9000 km/s, determined from narrow absorption features, the absorption minimum of the Si II 635.5-nm line is found to be blueshifted by about 14500 km/s. Cross-correlation with a library of supernova spectra using the "SuperNova IDentification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) indicates that 2010an is a few days before maximum brightness; narrow Na I D absorption is visible at the redshift of the host galaxy with an equivalent width of about 0.13 nm.

SN 2010ao (CBET 2211) is also a normal type-Ia supernova; after removal of the host-galaxy recession velocity of 6600 km/s, determined from narrow emission features, the absorption minimum of the Si II 635.5-nm line is found to be blueshifted by about 12700 km/s. SNID indicates that 2010ao is about two days before maximum light.

SN 2010au (CBET 2217) is also a type-Ia supernova, possibly of the SN 1999aa variety (e.g., Li et al. 2001, Ap.J. 546, 734) within about two days of maximum light, but the spectrum is noisy and heavily contaminated by host-galaxy starlight; after removing the host-galaxy recession velocity of 18300 km/s, determined from narrow emission features, the absorption minimum of the Si II 635.5-nm line is found to be blueshifted by about 10400 km/s.

The authors also confirm the findings by Cooke et al. (at website URL http://www.astronomerstelegram.org/?read=2491) and by Stritzinger et al. (CBET 2220) that 2010al (cf. CBET 2207) is a peculiar type-IIn supernova, similar to SN 1998S (Leonard et al. 2000, Ap.J. 536, 239), possibly as early as two weeks before maximum brightness according to SNID. The C III/N III and He II emission lines, resembling those in Wolf-Rayet stars, are stronger than the hydrogen Balmer emission lines. Also, some narrow absorption lines are visible, probably indicating a slow circumstellar wind.