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GCN Circular 277

GRB990316: simultaneous optical observation
1999-03-18T03:27:59Z (25 years ago)
Hye-Sook Park at LLNL <>
H.S. Park, L. Ott, R. Porrata (LLNL), G. Williams, D. Hartmann 
(Clemson Univ.) report on behalf of the LOTIS collaboration:
LOTIS obtained realtime images of GRB990316 (BATSE Trigger 7475).
LOTIS  started recording the first image 13.6 sec after the burst
(on the rising edge of the GRB light curve). The first image was taken
with a 30 s integration time, thus this image completely overlapped the
remainder of the GRB gamma-ray emission which lasted a total of ~40 sec.
The first image from one of our 4 cameras (each with 8.8 x 8.8 deg
field of view) covers > 98% of the BATSE 3 sigma (0.3 deg statistical +
1.6 deg systematic) error circle. The GRB location is further
constrained by an annulus derived from IPN data (GCN/IPN notice) 
that passes through the BATSE error circle in the image. 
We searched for optical transients in this image by 1) comparing
background images taken at later times and 2)comparing the stellar
objects in the image with objects in the Guide Star Catalog and Digital
Sky Survey images. We found one transient object at RA=147.54, 
DEC=-4.95 (J2000) near the edge of the IPN annulus with V~12.5 
brightness. This object was seen only in the first image. No object
is seen in the DSS image at this location. The second image was 
started after the gamma ray emission was over (at 55 sec after the 
start of the burst). We cannot rule out the possibility that this OT 
is a local effect rather than associated with the gamma ray burst. 
However, we encourage follow up observations at this location for 
possible afterglow observations.
Further analysis is in progress and associated data will be placed
on our web page.
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