2009CBET.1776....1M

H. Marion, University of Texas and Texas A&M University; P. Garnavich, University of Notre Dame; and P. Challis, Harvard-Smithsonian Center for Astrophysics (CfA), on behalf of the CfA Supernova Group, reports that spectra of 2009dc (cf. CBET 1762) were obtained with the NASA Infrared Telescope Facility (+ SPEX) on Apr. 18.6 UT. Optical spectra were also obtained on Apr. 18 and 19 UT by M. Calkins and W. Peters with the F. L. Whipple Observatory 1.5-m telescope (+ FAST). The combined spectra cover the wavelengths from 0.36 to 1.3 microns. The presence of a strong C II absorption at rest wavelength 658.0 nm (see CBET 1768) is confirmed, and C II at 723.4 nm is also detected. No absorption is seen to be associated with the C II line at 474.5 nm, and no significant C I lines are detected in the infrared (Marion et al. 2006, Ap.J. 645, 1392). Unlike with SN 2006gz (Hicken et al. 2007, Ap.J. 669, L17), the expansion velocities of Si II and C II in 2009dc differ by only 700 km/s, and the C II equivalent width (EW) is decreasing more slowly than in 2006gz. Combined with the slow expansion velocities, this suggests that SN 2009dc will be more luminous than 2006gz and may be similar to the suspected "super-Chandra" event 2003fg (Howell et al. 2006, Nature 443, 308). Note, however, that SN 2009dc shows strong, narrow Na I absorption lines from both the Galaxy (EW = 0.07 nm) and the host (EW = 0.12 nm), implying significant dust extinction.