[IAUC] CBET 958: 20070510 : SUPERNOVA 2007cf IN MCG +02-39-21

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                                                  Electronic Telegram No. 958
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 2007cf IN MCG +02-39-21
     S. Blondin, M. Modjaz, R. Kirshner, and P. Challis, Harvard-Smithsonian
Center for Astrophysics report that a spectrogram (range 350-740 nm) of
2007cf (cf. CBET 954), obtained by W. Peters on May 10.29 UT with the F. L.
Whipple Observatory 1.5-m telescope (+ FAST), shows it to be a type-Ia
supernova around one week past maximum light.  Cross-correlation with a
library of supernova spectra indicates that 2007cf is most similar to the
subluminous type-Ia supernova 1999by at 8 days past maximum.  Adopting a
recession velocity of 9873 km/s for the host galaxy (from Smith et al. 2004,
A.J. 128, 1558), the maximum absorption in the Si II line (rest 635.5 nm) is
blueshifted by roughly 9500 km/s.  Assuming that the galaxy is in the Hubble
flow and the supernova suffers negligible extinction, the discovery
magnitude of 17.9 corresponds to an absolute magnitude of roughly -17.8,
which confirms the subluminous nature of the event.
     J. M. Silverman, T. N. Steele, and A. V. Filippenko, University of
California, Berkeley, report that inspection of CCD spectra (range 330-1020
nm), obtained on May 10 UT with the Shane 3-m reflector (+ Kast spectrograph)
at Lick Observatory, shows that 2007cf is a type-Ia supernova approximately
1 week past maximum brightness.  Removing the host-galaxy recession velocity
of 9873 km/s (Smith et al. 2004, A.J. 128, 1558), the minimum of the Si II
635.5-nm absorption feature is found to be blueshifted by about 9300 km/s.


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                         (C) Copyright 2007 CBAT
2007 May 10                      (CBET 958)               Daniel W. E. Green