TITLE:   GCN CIRCULAR
NUMBER:  820
SUBJECT: GRB000926 : increasing optical decay slope
DATE:    00/09/30 00:47:57 GMT
FROM:    Johan U. Fynbo at ESO,Garching  <jfynbo@eso.org>

J. P. U. Fynbo, P. Moller (ESO), J. Gorosabel (DSRI, Copenhagen),
J. Hjorth, B. L. Jensen, and H. Pedersen (U. of Copenhagen), 
report on behalf of a larger European GRB Collaboration:

"Using the ALFOSC on the 2.5m Nordic Optical Telescope, we have
obtained further R-band imaging of the Optical Transient (OT) of 
GRB 000926 (GCN #801, #803, #804) on 2000 September 
29.84-29.95 UT.

We find the following R-band magnitudes of the OT using the 
reference star of Halpern et al. (GCN #806) :

UT          R-band    1sigma
-----------------------------
29.8414     21.779    0.042
29.9478     21.890    0.082

An updated lightcurve including the NOT measurements (black circles)
and the measurements of Halpern et al. (GCN #806), Price et al. (#811)
and Veillet (GCN ~818) (open diamonds) can be seen at
www.obs.aau.dk/~jfynbo/grb/grb000926/lightcurve.gif. The new NOT 
measurements fall below the extrapolation of the power-law decline
found at earlier epochs. We conclude therefore that the decay slope 
of the afterglow is increasing.