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GCN Circular 498

GRB 991216 Optical Observations
1999-12-19T12:15:14Z (24 years ago)
Brian Lindgren Jensen at U.of Copenhagen <>
B. L. Jensen, H. Pedersen, J. Hjorth, J. Pritchard (U. of Copenhagen),
T. Abbott (NOT), A. J. Castro-Tirado (LAEFF-INTA, Madrid), E. Pian
(ITESRE, Bologna), P. Vreeswijk (U. of Amsterdam) and J. Greiner (AIP,
Potsdam) report on behalf of a larger European collaboration:

"We have obtained R-band exposures of the optical counterpart
(GCN #472) using the Danish 1.5m at La Silla (Dec. 18) and the
2.5m Nordic Optical Telescope on La Palma (Dec. 19). When measured
relative to star "A" (GCN #476, #486) we obtain the following
Date (UT)      R               Exp    FWHM
Dec. 18.11 :  20.12 +-0.1     3x300s  1.8"
Dec. 18.32 :  20.40 +-0.1     3x300s  1.9"
Dec. 19.10 :  20.90 +-0.1     4x300s  1.8"  

When analyzed jointly with observations available from GCNs
(excluding the Rc~21.1 from GCN #487) we deduce a power-law
decay index of -1.17+-0.10. The corresponding plot is available at: ."
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