[IAUC] CBET 488: 20060427 : SUPERNOVA 2006bk

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                                                  Electronic Telegram No. 488
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 2006bk
     S. Blondin, M. Modjaz, R. Kirshner, and P. Challis,
Harvard-Smithsonian Center for Astrophysics, report that a spectrum
(range 350-740 nm) of SN 2006bk (cf. CBET 462, CBET 475), obtained on
Apr. 21.31 UT by W. Peters with the F. L. Whipple Observatory 1.5-m
telescope (+ FAST), shows it to be a type-Ia supernova, roughly three
weeks past maximum light.  SN 2006bk was classified as a type-Ic
supernova around maximum light in CBET 475, on the basis of a
"W-shaped" feature around 500 nm.  This feature is due to unresolved
blends of Fe II lines, and is common to both type-Ia and type-Ic
post-maximum spectra -- hence the possible confusion.  However,
cross-correlation with a library of supernova spectra shows that SN
2006bk is similar to the type-Ia supernova 1997br at 21 days past
maximum.  The best-match type-Ic spectrum is that of SN 1990B at 28
days past maximum; however, it does not concur well with all the
spectral features of SN 2006bk.  A comparison plot can be seen at the
following URL:  http://cfa-www.harvard.edu/oir/Research/supernova/
spectra/sn2006bk_comp.gif
     Blondin et al. add that another spectrum of SN 2006bk, obtained
on Apr. 23.33 by J. Hernandez (University of Michigan), shows the
spectrum to be similar to the type-Ia supernova 2000fa several weeks past
maximum, which confirms that SN 2006bk is a type-Ia supernova.


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                         (C) Copyright 2006 CBAT
2006 April 27                    (CBET 488)               Daniel W. E. Green