2011CBET.2656....2S

M. Stritzinger, Oskar Klein Centre, Stockholm University; N. Morrell, Las Campanas Observatory; J. Anderson, F. Foerster, and M. Hamuy, Universidad de Chile; G. Pignata, Universidad Andres Bello; and G. Folatelli, University of Tokyo; on behalf of the Millennium Center for Supernova Science, report that they have obtained spectra (range 432.5-965.9 nm) of these three supernovae on Mar. 5.1 UT with the Magellan I Baade 6.5-m telescope (+ IMACS) at Las Campanas Observatory. The spectrum of SN 2011X indicates that it is an evolved type-IIP supernova; best matches with the "Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666, 1024) suggest that 2011X is at least 3-4 months old. SN 2011Y is a normal type-Ia supernova around maximum light; adopting for the host galaxy a recession velocity of 20385 km/s (as derived by the SNID code, based on the spectral features of the supernova), an expansion velocity of 11000 km/s is computed from the absorption minima of the Si II 635.5-nm line.

SN 2011Z is a type-Ia supernova before maximum light. Cross-correlation with a library of supernova spectra using SNID provides a close match to the sub-luminous supernova 1986G (Phillips et al. 1987, PASP 99, 592). Adopting a SNID-derived host recession velocity of 6595 km/s, expansion velocities of 10500 km/s and 11000 km/s are derived from the absorption minima of the Si II 597.1- and 635.5-nm lines, respectively.