Electronic Telegram No. 974
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
URL http://www.cfa.harvard.edu/iau/cbat.html


SUPERNOVAE 2007cl AND 2007cm
     R. J. Foley, L.-B. Desroches, D. S. Wong, M. R. Moore, and A. V.
Filippenko, University of California, Berkeley, report that CCD spectra
(range 340-1040 nm), obtained on May 24 UT with the 3-m Shane telescope at
Lick Observatory, show that SN 2007cl (CBET 972) is of type Ic.  Although
its spectrum is similar to that of a type-Ia supernova past maximum light,
it lacks the S II doublet and is most similar to SN 1987M at about 7 days
past maximum (Filippenko, Porter, and Sargent, 1990, A.J. 100, 1575).
Removing the host-galaxy recession velocity of 6650 km/s (Falco et al.
1999, PASP 111, 438), the minimum of the 635.5-nm Si II absorption is
blueshifted by about 9000 km/s.
     Also, SN 2007cm (CBET 973) is of type IIn:  A very blue continuum
with low-equivalent-width hydrogen emission lines suggests that 2007cm
is a young object.  At a distance of 70 Mpc (Abazajian et al. 2005, A.J.
129, 1755), its absolute magnitude is -16.7, indicating that 2007cm is a
true supernova explosion and not a "supernova imposter" (Van Dyk et al.
2006, http://arxiv.org/abs/astro-ph/0603025).


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2007 CBAT
2007 May 26                      (CBET 974)               Daniel W. E. Green