TITLE: GCN GRB OBSERVATION REPORT NUMBER: 820 SUBJECT: GRB000926 : increasing optical decay slope DATE: 00/09/30 00:47:57 GMT FROM: Johan U. Fynbo at ESO,Garching 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.