2005CBET..132....1M

M. Modjaz, R. Kirshner, and P. Challis, Harvard-Smithsonian Center for Astrophysics, report that a spectrum (range 340-730 nm) of SN 2005bc (cf. IAUC 8504), obtained on Apr. 3.33 UT by P. Nutzman with the F. L. Whipple Observatory 1.5-m telescope (+ FAST), shows it to be a type-Ia supernova with a spectral-feature age (cf. Riess et al. 1997, A.J. 114, 722) of about 3 (± 2) days before maximum light. The supernova expansion velocity, derived from the minimum of Si II (rest 635.5 nm) and adopting the NED recession velocity of 3679 km/s for the host galaxy, is about 12000 km/s. A higher-S/N spectrogram taken by Nutzman on Apr. 4.33 confirms the classification and exhibits Si II absorption at 580 nm (rest 597.9 nm) that is stronger than usual, relative to the Si II absorbtion at 610 nm (rest 635.5 nm), suggesting that this supernova might be less luminous than a normal type-Ia supernova. Interstellar Na I D absorption at the redshift of the host galaxy with an equivalent width of about 0.2 nm is detected, indicating gas along the line-of-sight in the host galaxy and thus suggesting reddening by dust.