[IAUC] CBET 1304: 20080318 : SUPERNOVAE 2008bc AND 2008bd

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                                                  Electronic Telegram No. 1304
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
M.S. 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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CBAT en CFA.HARVARD.EDU (science)
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SUPERNOVAE 2008bc AND 2008bd
     G. Folatelli, G. Pignata, M. Hamuy, and J. Maza, Universidad de Chile,
on behalf of the Millenium Center for Supernova Studies, report that a
spectrogram (range 350-920 nm) of 2008bc (cf. CBET 1301), obtained on Mar.
14.0 UT with the European Southern Observatory 3.6-m telescope (+ EFOSC2) at
La Silla, shows this to be a young type-Ia supernova about a week before
maximum light.  Cross-correlation with a library of supernova spectra using
the "Supernova Identification" code (SNID; Blondin and Tonry 2007, Ap.J. 666,
1024) provides the best match to SN 2003du (Stanishev et al. 2007, A.Ap. 469,
645) at ten days before maximum.  Adopting the NED recession velocity of 4523
km/s for the host galaxy (Strauss et al. 1992, Ap.J. Suppl. 83, 29), the
minimum absorption of the Si II 635.5-nm line indicates an expansion velocity
of about 14000 km/s.  The spectrum does not show significant absorption due
to Na I D at the redshift of the host galaxy.
     A spectrogram of 2008bd (cf. CBET 1301), obtained as above on Mar. 14.1,
shows this to be a type-Ia supernova similar to SN 1991bg a few days after
maximum.  Comparison with a library of supernova spectra provides the best
match to SN 2005bl (Taubenberger et al., http://lanl.arxiv.org/abs/0711.4548)
at five days after maximum.  Adopting the NED recession velocity of 9025 km/s
for the host galaxy (da Costa et al. 1998, A.J. 116, 1), the minimum
absorption of the Si II 635.5-nm line indicates an expansion velocity of about
9300 km/s.  The spectrum does not show significant absorption due to Na I D
at the redshift of the host galaxy.


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                         (C) Copyright 2008 CBAT
2008 March 18                    (CBET 1304)              Daniel W. E. Green