2008CBET.1424....1B

S. Blondin, Harvard-Smithsonian Center for Astrophysics (CfA), on behalf of the CfA Supernova Group, reports that a spectrogram (range 350-740 nm) of 2008dt (cf. CBET 1423), obtained by P. Berlind on July 1.21 UT with the F. L. Whipple Observatory 1.5-m telescope (+ FAST), shows it to be a type-Ia supernova around one week before maximum light. The Si II line (rest 635.5 nm) has an extremely broad absorption profile, suggestive of a high-velocity component. Cross-correlation with a library of supernova spectra using the Supernova Identification code (Blondin and Tonry 2007, Ap.J. 666, 1024) indicates that 2008dt is most similar to the type-Ia supernova 2005cf at 11 days before maximum, which also displayed high-velocity features (Garavini et al. 2007, A.Ap. 471, 527). Adopting a recession velocity of 10637 km/s for the host galaxy (from The Updated Zwicky Catalog, http://tdc-www.harvard.edu/uzc/), the maximum absorption in the Si II line (rest 635.5 nm) is blueshifted by roughly 14000 km/s. Also, interstellar Na I D absorption at the redshift of the host galaxy is visible in the spectrum with an equivalent width of roughly 0.1 nm.