[IAUC] CBET 570: 20060705 : SUPERNOVA 2006dm IN MCG -01-60-21

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                                                  Electronic Telegram No. 570
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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SUPERNOVA 2006dm IN MCG -01-60-21
     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.


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                         (C) Copyright 2006 CBAT
2006 July 5                      (CBET 570)               Daniel W. E. Green