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GCN Circular 325

Subject
GRB 990510: optical observation
Date
1999-05-14T00:45:00Z (25 years ago)
From
Gabriele Ghisellini at Obs.Astro. di Brera <gabriele@merate.mi.astro.it>
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, 
DEC=-80:29:11.7). 
This suggests that the faint source is not the host galaxy of the GRB.
See in  http://www.merate.mi.astro.it/~lazzati/GRB990510/  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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