2006CBET..570....1S

J. Selj, D. Sharapov, A. Somero, L. Oestman, and J. Sollerman, on behalf of the NORDFORSK/NOT Summer School in Observational Astrophysics; and S. Blondin, Harvard-Smithsonian Center for Astrophysics, report on spectroscopy of SN 2006dm (cf. CBET 568) obtained with the Nordic Optical Telescope (+ ALFOSC; range 350-900 nm, resolution 0.8 nm) on July 5.1 UT. A full reduction of the spectrum of 2006dm confirms the identification of Filippenko et al. (cf. CBET 569) that this is a type-Ia supernova before maximum light. Cross-correlation with a library of supernova spectra shows that SN 2006dm is most similar to the subluminous type-Ia SN 2000dk (cf. IAUC 7493, 7494) at -4 days. The best-match "normal" type-Ia supernova, 1999cc (cf. IAUC 7163, 7169) at -3 days, fails to reproduce the strength of the Si II absorption at 580 nm, as noted by Filippenko et al. (see a comparison plot at http://cfa-www.harvard.edu/oir/Research/supernova/spectra/sn2006dm_comp.gif). Adopting a recession velocity of 6849 km/s for the host galaxy (from de Vaucouleurs et al. 1991, Third Ref. Cat. of Bright Galaxies, ver. 3.9), the maximum absorption in the Si II line (rest 635.5 nm) is blueshifted by roughly 12000 km/s.