Electronic Telegram No. 133
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)
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SUPERNOVA 2005bg IN MCG +03-31-93
     R. Quimby, P. Mondol, F. Castro, M. Sellers, P. Hoeflich,
and J. C. Wheeler, University of Texas; and C. Gerardy, Imperial
College, report the discovery of a supernova in unfiltered CCD
images taken with the 0.45-m ROTSE-IIIb telescope at McDonald
Observatory on Mar. 28.17 (with the new object at mag about 16.2)
and Apr. 2.16 UT (mag about 16.1).  SN 2005bg is located at R.A.
= 12h17m17s.18, Decl. = +16o22'17".6 (equinox 2000.0), which is
0".6 north and 0".4 east of the core of MCG +03-31-93.  The new
object was found by subtracting a co-addition of images taken
between 2004 Dec. 11 and 2005 Jan. 17 (limiting mag about 18.6);
a similar subtraction showed nothing at this location on Mar.
20.19 (limiting mag about 17.2).  A spectrum (range 430-890 nm)
of the new object, obtained on Apr. 7.13 with the 9.2-m
Hobby/Eberly Telescope (+ Marcario Low-Resolution Spectrograph) by
B. Roman and S. Rostopchin, shows it to be a type-Ia supernova.
Assuming the NED host-galaxy recession velocity of 6921 km/s, the
expansion velocity derived from the minimum of the Si II 635.5-nm
feature is 11000 km/s.  The spectrum also shows Mg II 448.1-nm, Fe
II 508.3-nm, and S II 545.4- and 564.0-nm lines; however, the Ca
II infrared triplet is not detected.  Additional unfiltered CCD
magnitudes for SN 2005bg:  Apr. 3.16 UT, 15.8; 5.15, 15.6.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
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                         (C) Copyright 2005 CBAT
2005 April 8                     (CBET 133)               Daniel W. E. Green