[IAUC] CBET 927: 20070419 : SUPERNOVA 2007bg

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                                                  Electronic Telegram No. 927
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 2007bg
     Further to IAUC 8622, R. Quimby, University of Texas; and E. Rykoff
and F. Yuan, University of Michigan, report the discovery of an apparent
supernova in unfiltered CCD images taken around Apr. 16.15 (at mag about
17.7), and 18.15 UT (mag about 17.8) using the 0.45-m ROTSE-IIIb
telescope at the McDonald Observatory.  The new object was also detected
at mag about 17.7 on Apr. 16.81 in unfiltered CCD images from the
ROTSE-IIId telescope in Bakirlitepe, Turkey.  SN 2007bg is located at
R.A. = 11h49m26s.18, Decl. = +51o49'21".8 (equinox 2000.0), which is
coincident with a faint, uncatalogued source in the Sloan Digital Sky
Survey.  Nothing was present at this location in ROTSE-IIIb images taken
around Apr. 6.15 (limiting magnitude about 18.2), nor in a co-addition of
ROTSE-IIIb images taken between 2004 Dec. 11 and 2006 Dec. 27 (limiting
mag about 20.5).
     A spectrum (range 420-890 nm) of 2007bg, obtained on Apr. 18.30 UT
with the 9.2-m Hobby-Eberly Telescope (+ Marcario Low-Resolution
Spectrograph) by H. Edelmann and E. Terrazas, shows it to be a type-Ic
supernova.  Narrow emission lines seen in the spectrum correspond to
H-alpha and O III 500.7-nm, redshifted by z about 0.034.  The spectrum is
similar to that of SN 2002ap at around 11 days after maximum, although
for 2007bg the absorption around 610 nm is significantly stronger, and
the O I 777-nm absorption is much weaker.  Despite the comparatively
strong 610-nm absorption, the lack of any discernable S II 545- or 562-nm
features supports the clasification as a type-Ic supernova.  At this
redshift, the ROTSE-III photometry corresponds to an absolute magnitude
of about -18.0.


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                         (C) Copyright 2007 CBAT
2007 April 19                    (CBET 927)               Daniel W. E. Green