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GCN Circular 325

GRB 990510: optical observation
1999-05-14T00:45:00Z (25 years ago)
Gabriele Ghisellini at Obs.Astro. di Brera <>
D. Lazzati, S. Covino and G. Ghisellini, of the Observatory of Brera 
(Milan, Italy) report:

In the 600 s VLT-FORS1 image taken at May 11.13509 with 1.2" seeing, the 
faint source 2.1" south of the OT of GRB990510 is completely consistent 
with being a pointlike object, 2.86+-0.02 mag (in the R band) fainter 
than the source located 3.9" north, 0.8" west of the OT.
At this time the latter source and the OT had the same magnitude,
R=19.10+-0.02 (assuming R=16.5 for the USNO star at RA = 13:38:00.82, 
This suggests that the faint source is not the host galaxy of the GRB.
See in  the original 
image, the image with the OT subtracted, and the residuals after having 
subtracted also the faint object, assuming it is a point source.

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