TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2693 SUBJECT: Very bright burst detected from SGR 1806-20 DATE: 04/09/04 09:25:41 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and T. Cline on behalf of Konus-Wind team, G. Ricker, J-L Atteia, N. Kawai, D. Lamb, S. Woosley, J. Doty, R. Vanderspek, J. Villasenor, G. Crew, N. Butler, J.G. Jernigan, F. Martel, G. Prigozhin, A. Dullighan, J. Braga, R. Manchanda, G. Pizzichini, Y. Shirasaki, C. Graziani, M. Matsuoka, T. Tamagawa, T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, T. Donaghy, C. Barraud, M. Boer, J-F Olive, and J-P Dezalay, on behalf of the HETE GRB team, and K. Hurley on behalf of the IPN team report: A very bright SGR burst was detected by Konus-Wind on August 28 at 42581.338 s UT. This burst also triggered HETE at 42569.952 s UT (H3514). We have triangulated it to an annulus centered at RA(2000) = 317.135 deg, Decl(2000) = -17.624 deg, whose radius is 42.448 +/- 1.601 deg (3 sigma). As this annulus includes the position of SGR 1806-20 and Konus ecliptic latitude response indicates that the burst source lays near ecliptic plane, we believe that SGR 1806-20 is the source of this event. As observed by Konus-Wind, the burst had a duration of 0.7 s, a fluence ~4.0x10^-5 erg/cm^2, and a peak flux ~1x10^-4 erg/cm^2 s (both in 20-200 keV range). The value of the spectral parameter kT for an OTTB spectral model (dN/dE ~ E^{-1} exp(-E/kT)) was 26 keV. This burst is the brightest one from this SGR detected so far by Konus-Wind. It is stronger, than the burst on 040825 (GCN 2665) by a factor of about 1.7 in fluence and peak flux.