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GCN Circular 397

GRB 990806, Optical Observations
1999-08-08T23:59:42Z (25 years ago)
Jonathan Kemp at Biosphere 2 Ctr/Columbia U <>
J. Kemp, R. Uglesich, N. Mirabal, J. Halpern (Columbia),
D. Harkavy (Harvard), E. Costa (IAS/CNR, Rome) report 
on behalf of the BeppoSAX team and the MDM Observatory 
GRB follow-up team's southern extension:

"We reobserved the BeppoSAX WFC error circle of GRB 990806
(Piro GCN 392; Gandolfi GCN 393) in the R band using the CTIO 0.9m.
A total exposure of 180 minutes was obtained starting on
Aug. 8.31 UT.  Seeing was 1".3.  The 5-sigma limiting magnitude
of the summed R-band image is 23.8.  No variable object is
detected in comparison with images obtained on the previous night
(GCN 395).  Using a sensitive difference imaging technique,
we set a limit of R > 23.3 on Aug. 7.3 for any fading optical 
transient in the WFC error circle.  This is consistent with the 
R-band limit of 23.5 set by the ESO 2.2m (Greiner et al. GCN 396).

The new image is posted at

This message may be cited."
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