TITLE: GCN CIRCULAR NUMBER: 8471 SUBJECT: GRB 081102: MASTER prompt optical limit DATE: 08/11/03 20:06:42 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs MASTER-Net Team (http://observ.pereplet.ru): V. Lipunov, V.Kornilov, E.Gorbovskoy, A.Belinski, N.Shatskiy, N.Tyurina, D.Kuvshinov, P.Balanutsa Sternberg Astronomical Institute, Moscow State University A. Tlatov, A.Parkhomenko Kislovodsk Solar Station of the Pulkovo observatory V.Krushinski, I.Zalognikh Ural State University, Kourovka S.Yazev, K.Ivanov Irkutsk State University MASTER Very Wide Field Camera located at Kislovodsk (2000 m) (http://apollo.sai.msu.ru/, D=50 mm, 4x1000 square degrees, 35'' per pix) has observed the Swift-BAT GRB081102 error box (Ukwatta et al., GCN Circ 8642) with 5s exposures during all night without windows between images. There are two separeted (~702m) mount with double cameras. Now we present results from North camera. These unfiltered images are calibrated relative to Tycho stars (V). We do not detect any new source at the XRT position reported in GCN Circ. 8467 ( Osborne et al.) brighter than 12.4 mag before and after trigger time. The photometry results +-4 min around trigger time: T-T_trigger m_lim (S/N=3) Exposure Coadd -255s... 0... 255 s 11.6 5s no -2min...0...+2 min 12.2 30s 6 -2min...0...+2 min 12.4 60s 12 The optical fluence during the 60s-GRburst is limited by <= 6x10_-9 erg/cm_2 including 2.5 magnitude absorbtion (Ukwatta et al., Circ 8462). The BAT-fluence is aboute 3 10_-6 erg/cm_2 (15-150 Kev) (http://gcn.gsfc.nasa.gov/notices_s/333427/BA/). So Optical Fluence/Gamma-Fluence ~ < 1/500 Same ratio for GRB080319B is ~ 1/200 (Naked Eye GRB). The light curve is available at http://observ.pereplet.ru/images/GRB081102/lc1.png The video are available at http://observ.pereplet.ru/images/GRB081102/grb.gif You can see 200 sets. Note: the GRB was at the edge of the FOW. The reduction is continuing. mailto: lipunov@sai.msu.ru