TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  328
SUBJECT: GRB990510, VI observations
DATE:    99/05/14 15:02:30 GMT
FROM:    Andrzej Udalski at Warsaw U. Observatory  <udalski@sirius.astrouw.edu.pl>

G. Pietrzynski and A. Udalski (Warsaw University Observatory) report on
behalf of the OGLE microlensing survey team:

We continued VI-band observations of the optical counterpart of GRB
990510 on May 12/13, 1999 (seeing about 1.8") and May 13/14, 1999
(seeing about 1.1") with the 1.3-m Warsaw telescope at the Las Campanas
Observatory (Chile). We report the following brightness of the object as
measured in images composed of a few 600 sec exposures:

   UT        JDhel.      No of 600s    Band     Magnitude  Error
May 1999    -2450000      exposures

13.3423    1311.84493       3           I         21.05     0.13
13.3684    1311.87104       3           V         21.86     0.08
13.9980    1312.49533       3           I         21.17     0.13
14.0267    1312.52935       5           V         22.41     0.06
14.1854    1312.68804       4           I         21.35     0.07
14.2294    1312.73198       4           V         22.46     0.05

We confirm that the object located about 2" south from the optical
counterpart of GRB990510 is rather a regular star (cf  Lazzati et al,
GCN, #325) than the host galaxy. Its point-like character is clearly seen
in summed images and its photometry yields: V=22.54+/-0.06 and
I=21.33+/-0.07. 

Updated photometry of the optical counterpart of GRB 990510 and light
curves are available from the OGLE Internet archive: 

http://www.astrouw.edu.pl/~ftp/ogle