Circular No. 7164
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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GRB 990510
     J. Kaluzny, Warsaw University Observatory (WUO); P. M.
Garnavich and K. Z. Stanek, Harvard-Smithsonian Center for
Astrophysics; W. Pych, WUO; and I. Thompson, Carnegie Observatories,
write: "We observed the optical transient found in the error box of
GRB 990510 (IAUC 7160) by Vreeswijk et al. (GCN 310) with the 1.0-m
Swope telescope at the Las Campanas Observatory between May 11.0
and 11.4 UT.  We measure the following precise position for the
transient:  R.A. = 13h38m07s.64, Decl. = -80o29'48".8 (equinox
2000.0; uncertainty +/- 0".3), based on the Guide Star Catalog.  We
find that the object declined steadily in the R band over the
observing period and, combined with data from Galama et al. (GCN
313), the light curve is consistent with a power law in time with
an exponent of -0.89.  There is a suggestion that the slope may be
becoming steeper.  A comparison star of mag R = 16.5 (position end
figures 00s.82, 11".7) in the USNO A2.0 catalogue gives R = 18.9
for the optical transient on May 11.0.  We find the R magnitudes in
this region of the USNO catalogue to be of dubious quality,
especially fainter than 16.5.  Adding the R-band exposures taken in
about 1" seeing reveals an object 1".8 south of the optical
transient and about 3 mag fainter; this may be the host galaxy."
     G. Pietrzynski and A. Udalski, Warsaw University Observatory,
report on behalf of the OGLE microlensing survey team:  "We
monitored the optical counterpart, starting on May 10.992 UT, with
the 1.3-m Warsaw telescope at the Las Campanas Observatory.  In
total, 17 V-band and 21 I-band frames were collected, covering
about 10.25 hr (exposure times 900 and 600 s for the V and I-band
frames, respectively).  The object is apparently variable -- its
brightness faded by about 0.6 mag in the course of the night, from
19.45 to 20.05 in V and from 18.50 to 19.15 in I.  Photometry of
the optical counterpart of GRB 990510 and VI light curves are
available from the OGLE Internet archive at
http://www.astrouw.edu.pl/~ftp/ogle."


COMET C/1998 M5 (LINEAR)
     Visual m_1 estimates:  Apr. 2.76 UT, 9.8 (A. Baransky, Kiev,
Ukraine, 0.20-m reflector); 11.82, 9.5 (M. Reszelski, Szamotuly,
Poland, 20x60 binoculars); 18.83, 10.6 (M. Meyer, Frauenstein,
Germany, 0.25-m reflector); 21.06, 9.6 (K. Hornoch, Lelekovice,
Czech Republic, 10x80 binoculars); May 3.90, 11.1 (R. J. Bouma,
Groningen, The Netherlands, 0.25-m reflector); 9.85, 11.0 (M.
Lehky, Hradec Kralove, Czech Republic, 25x100 binoculars); 11.10,
11.0 (J. Bortle, Stormville, NY, 0.41-m reflector).

                      (C) Copyright 1999 CBAT
1999 May 11                    (7164)            Daniel W. E. Green