Electronic Telegram No. 843
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)
URL http://cfa-www.harvard.edu/iau/cbat.html


POSSIBLE RADIO SUPERNOVA IN NGC 3628
     W. Li, University of California at Berkeley, reports that analysis
of the KAIT optical-monitoring data of NGC 3628 during the course of the
Lick Observatory Supernova Search program (e.g., IAUC 6627; Filippenko
2001, ASP Conf. Ser. 246, 121) does not reveal an apparent new object at
the position of the possible radio supernova reported on CBET 842, to the
following 3-sigma limiting magnitudes:  2006 Jan. 8.59 UT, [18.8; 23.50,
[18.7; Feb. 7.42, [19.1; May 3.25, [19.3; 11.25, [18.0; Dec. 18.57,
[18.8; 2007 Jan. 18.44, [18.8, 26.51, [19.1.  In particular, the 2006
Dec. 18.57 image (nearly contemporary with the radio detections) limits
any optical supernova to be fainter than absolute magnitude -11.5
(assuming a distance of 11.4 Mpc to NGC 3628, which is the Cepheid
distance to NGC 3627, the other member of the Leo Triplet; cf. Saha et al.
1999, Ap.J. 522, 802).  The position for the radio transient also falls on
the apparent central dust lane in NGC 3628.  Thus, any supernova is likely
to be heavily obscured by dust, or intrinsically faint, or both.


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
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                         (C) Copyright 2007 CBAT
2007 February 14                 (CBET 843)               Daniel W. E. Green