2006CBET..351....1M

M. Modjaz, R. Kirshner, P. Challis, and S. Blondin, Harvard-Smithsonian Center for Astrophysics, report that spectra (range 350-740 nm) of SN 2005mz (CBET 347) and of SN 2005na (CBET 350), obtained on Jan. 3.13 and 4.34 UT (respectively) by P. Berlind with the F. L. Whipple Observatory 1.5-m telescope (+ FAST), show them to be type-Ia supernovae, with spectral-feature ages (Riess et al. 1997, A.J. 114, 722) of about 3 and 1 (± 2) days before maximum light, respectively. Adopting recession velocities of 5264 and 7891 km/s for the host galaxies of 2005mz and 2005na, respectively (both from Falco et al. 1999, PASP 111, 438), the maximum absorption in the Si II line (rest 635.5 nm) is blueshifted by about 11000 km/s in both supernovae. The spectrum of SN 2005mz exhibits strong Si II (rest 597.2 nm) and is similar to spectra of SN 1999by (Garnavich et al. 2004, Ap.J. 613, 1120) taken a few days before maximum, indicating that this may be a subluminous event.