TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5632 SUBJECT: GRB 060926: MASTER: first minutes decay DATE: 06/09/27 15:54:15 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, D.Kuvshinov, N.Tyurina, A.Belinski, E.Gorbovskoy, A.Krylov, G.Borisov, A.Sankovich, V.Vladimirov, P.Gritsyk Sternberg Astronomical Institute, Moscow Union 'Optic' MASTER robotic system (http://observ.pereplet.ru) responded to GRB060926 (Holland et al., GCN Circ 5612) under the good conditions. The first image was started at 2006-09-26 16:49:57 UT, 76 s after the GRB time (355 mm telescope, 6 square degrees FOV, 2.1'' per pix, CCD Alta U16). The unfiltered image is calibrated relative to USNO A2.0 (0.8 R + 0.2 B). We find faint OT on the first and on the coadded images at position: aplha = 17 35 43.66 dec = 13 02 18.3 err = +- 0.7'' wich coincided with the Holland et al.(GCN Circ 5612) OT position. Our results: T-T_grb mean time exp_time m (close to R) S/N 76 s - 106 s 91 s 30 s 17.5+-0.3 4.5 76 s - 360 s 218 s 5x30 s 18.2+-0.3 4 76 s - 820 s 448 s 10x30 s 18.3+-0.3 4 76 s - 1411 s 743 s 15x30 s 18.7+-0.3 4 1024 s - 1810 s 1417 s 10x30 s >19.7 We fitted these values with a powerlaw with a decay index of 0.69 up to 743 s. This is steeper then the powerlaw OPTIMA-Burst observations (GCN 5623, A. Stefanescu et al.). The light curve is available at http://observ.pereplet.ru/images/GRB060926/lc.jpg . JPG-Images are available. Small part with OT: First - http://observ.pereplet.ru/images/GRB060926/GRB060926_1.jpg Sum of 5 - http://observ.pereplet.ru/images/GRB060926/GRB060926_5.jpg Sum of 10 - http://observ.pereplet.ru/images/GRB060926/GRB060926_10.jpg The 2005 MASTER Survey Image http://observ.pereplet.ru/images/GRB060926/GRB060926_2005.jpg Full images: http://pereplet.sai.msu.ru/nauka/i12.jpg http://pereplet.sai.msu.ru/nauka/i12a.jpg http://pereplet.sai.msu.ru/nauka/i12b.jpg This work is supported by RFFI 04-02-16411 grant. This message can be cited. Mailto: lipunov@sai.msu.ru