TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3726 SUBJECT: GRB 050801: ROTSE-III Early Afterglow Break DATE: 05/08/01 19:50:15 GMT FROM: Eli Rykoff at U of Michigan/ROTSE E.S. Rykoff (U Mich), S.A. Yost (U Mich), W. Rujopakarn (U Mich), H. Swan (U Mich), K. Alatalo (Berkeley), R. Quimby (U Texas) report on behalf of the ROTSE collaboration: ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, is observing the optical counterpart to GRB 050801 (Swift trigger 148522, Band et al, GCN 3725). The early afterglow reported in GCN 3723 is characterized by a broken power-law, which does not decay significantly from t+21s to t+200s, followed by a decline with a power law index of ~-1.1. Our preliminary photometry, relative to the USNO A2.0 catalog, also shows some possible sub-structure to the lightcurve. tstart-tburst exptime mag --------------------------------- 21.8 5.0 14.99+/-0.06 203.0 20.0 15.01+/-0.03 1590.3 60.0 17.29+/-0.15