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IAUC 6899: 1998bu; GRB 980425

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                                                 Circular No. 6899
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 1998bu IN NGC 3368
     Mirko Villi, Forli, Italy, reports his discovery on CCD images
taken on May 9.9 UT of an apparent supernova (mag about 13) located
about 60" north of the center of NGC 3368 = M96.  Villi notes that
a previous CCD image taken on Apr. 21.9 shows no object in this
position, neither is anything visible on several atlases of galaxy
images.  S. Nakano, Sumoto, Japan, reports that M. Aoki (Toyama)
has obtained a CCD image of SN 1998bu (V = 11.8) on May 10.618 with
a 0.43-m reflector in bad weather conditions, from which the
following precise position was measured:  R.A. = 10h46m46s.03, Decl.
= +11o50'07".1 (equinox 2000.0), which is 4".3 east and 55".3 north
of the center of NGC 3368.  No star was visible on previous frames
of this galaxy taken by Aoki.  B. A. Skiff, Lowell Observatory,
reports that he viewed the apparent supernova on May 10.33 UT at
visual mag perhaps 12.0-12.5.  D. Hanzl, Brno, Czech Republic,
reports that he imaged SN 1998bu on May 10.835 at V = 12.37 with a
0.40-m reflector + CCD; he gave the offset as 49" north of the
galaxy's center.


GRB 980425
     J. S. Bloom, California Institute of Technology (CIT); D.
Frail, National Radio Astronomy Observatory; and S. R. Kulkarni,
CIT, report on behalf of the CIT gamma-ray burst team:  "Using the
2.54-m reflector at Las Campanas, S. Vogel and M. Regan obtained V,
R, and I images of the field of GRB 980425 (IAUC 6884) near the
presumed supernova discovered by Galama et al. (IAUC 6895, 6898).
Using the secondary standards of Lidman et al. (IAUC 6895), we
determine that the transient has continued to brighten, with the
following derived magnitudes (+/- 0.05):  May 8.311 UT, V = 13.87;
8.306, R = 13.84; 8.309, I = 13.98.  The error comes predominately
from the zero-point uncertainty.  The contribution to the flux from
a nearby star about 4".9 to the northwest and the host galaxy is
negligible (< 0.02 mag).  A composite light curve from published
fluxes can be obtained at
http://astro.caltech.edu/~jsb/ltcurve_980425.ps.  It is still
unclear as to the connection between the presumed supernova and GRB
980425.  In order to correlate the time of both, an accurate light
curve must be obtained."

                      (C) Copyright 1998 CBAT
1998 May 10                    (6899)            Daniel W. E. Green

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