TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3886 SUBJECT: GRB050824: First 2 hours of power low optical decay? DATE: 05/08/26 17:27:26 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, N.Tyurina, A.Belinski, E.Gorbovskoy, D.Kuvshinov Sternberg Astronomical Institute, Moscow Union "Optic" We have analysed all photometric points obtained during first 2 hours (see picture http://observ.pereplet.ru/images/GRB050824/2.jpg ) from ROTSE (GCN Circ 3867), MASTER (GCN Circ 3883), J. Gorosabel et al. (GCN Circ 3865) and Swift UVOT(GCN Circ 3880) in similar colors . The upper limits of ROTSE and MASTER for 500-750 sec (GRB time) are in agreement. Both instrumental systems are more or less similar. There is some contradiction with J. Gorosabel et al. (GCN 3865) and MASTER data (GCN Circ 3880) for 24 - 47 minutes. But there is no error bar in J. Gorosabel et al.(GCN 3865). The SWIFT UVOT V-band is most closed to MASTER in color sense. If we include only 2 MASTER points and Swift UVOT V-point we can obtain next power low: m = 2.1(+-0.2) log (t) + 19.5 , t in hours. This corresponds to usual flux power law F ~ t^-0.9 However there is strong contradiction with ROTSE (11 min) uper limit and J. Gorosabel et al. (GCN 3865) point. JPG-images are available at http://observ.pereplet.ru/images/GRB050824/2.jpg . This work is supported by RFFI 04-02-16411 grant. This message can be cited. Mailto: lipunov@sai.msu.ru