TITLE: GCN CIRCULAR NUMBER: 9252 SUBJECT: GRB 090424: MASTER-Net prompt optical limit DATE: 09/04/25 20:29:42 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs E. Gorbovskoy, V. Lipunov, V.Kornilov, A.Belinski, N.Shatskiy, N.Tyurina, D.Kuvshinov, P.Balanutsa, V.V.Chazov, P.V.Kortunov, A.Kuznetsov Sternberg Astronomical Institute, Moscow State University K.Ivanov, S.Yazev Irkutsk State University A. Tlatov, A.V. Parhomenko, Kislovodsk Solar Station of the Pulkovo Observatory V.Krushinski, I.Zalognikh, T.Kopytova Ural State University, Kourovka There are 6 MASTER Very Wide Field cameras located at Kislovodsk and Irkutsk with common FOW = 6000 square degrees (http://observ.pereplet.ru/). One of the two MASTER Very Wide Field Cameras located at Irkutsk (D=50 mm, 2x1000 square degrees, 11 Mpx, 72" per pix in binning regime) has observed UVOT error box (Cannizzo et al., GCN 9223) with 1s exposure befoure, during and after GRB Time without time gap between images. The error box is near at the center of our FOW. Our unfiltered images are calibrated relative to Tycho stars (V) and very close to V band. The magnitude limit of the each emage is ~8 m at the center of FOW (some cloudy on the sky). The limit of coadded six images ~ 9 m. We do not detect OT. Our observations results: ---------------------------------------------------------------------- Fermi GRB Trigg.* Exposure Mag Limit Optical Flux Coadd? time (sec) (sec) (m) (erg/sm^2 s) ---------------------------------------------------------------------- -2 1 8.1 1.3x10^-8 No -1 1 8.1 1.3x10^-8 No 0 1 8.0 1.4x10^-8 No +1 1 8.0 1.4x10^-8 No +2 1 8.0 1.4x10^-8 No +3 1 7.9 1.5x10^-8 No +4 1 8.0 1.4x10^-8 No +5 1 8.0 1.4x10^-8 No -60 : +120 1 ~8 ~1.4x10^-8 No -6 6 8.9 7.0x10^-9 Yes +0 6 8.7 7.3x10^-9 Yes +6 6 8.8 7.2x10^-9 Yes +12 6 8.9 7.0x10^-9 Yes -60 60 9.7 3.0x10^-9 Yes 0 60 9.7 3.0x10^-9 Yes 60 60 9.5 3.5x10^-9 Yes ----------------------------------------------------------------------- *Fermi GBM Trigger Time = 14:12:08.67 (Connaughton, GCN 9230) 1% coincident with our start zero image time. 1). the optical fluence during GRBurst is limited by 0 up to +6 s ~<= 1 x 10E-7 erg/cm^2 0 up to +60 s <= 5 x 10E-7 erg/cm^2 including total absorbtion 1 magnitude in V band. (The absorption column density NH = (0.20 +/- 0.01) x10^22 cm^-2 from Swift XRT spectrum data, Margutti, GCN 9237). The event fluence (8-1000 keV) in this time interval is (5.2 +/- 0.1)E-05 erg/cm^2 (Connaughton, GCN 9230). So: 2). Optical-Fluence(6s)/Gamma-Fluence (8-1000 keV) ~ < 1/500 Optical-Fluence(60s)/Gamma-Fluence(8-1000 keV) ~ < 1/100 The same ratio for GRB080319B is Optical-Fluence/Gamma-Fluence(8 - 1000 keV) ~ 1/140 (Naked Eye GRB, Racusin, Karpov et al., Nature, vol.455, 183, 2008). The light curve and film of our observations is available at http://observ.pereplet.ru/images/GRB090424/GRB090424.html The reduction is continued. The message may be cited. mailto: lipunov@sai.msu.ru