TITLE: GCN CIRCULAR NUMBER: 4312 SUBJECT: An extraordinary long burst on December 3 from SGR1806-20 DATE: 05/12/06 15:48:11 GMT FROM: Valentin Pal'shin at Ioffe Inst S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and T. Cline on behalf of the Konus-Wind team, S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm on behalf of the Swift team, A bright extraordinary long SGR-like event triggered the Konus-Wind at T0=42203.684 s UT (11:43:23.684) on December 3. This burst was also observed by Swift-BAT out of the BAT field of view. The measured time delay between the burst arrival times on the two s/c is 5.245-5.276 sec (3 sigma confidence range). For the SGR 1806-20 position the expected time delay is 5.274 sec. As the measured time delay is consistent with the expected for the position of SGR 1806-20, we conclude that this burst originated from it. But we should notice that the measured time delay also consistent with the SGR 1801-23 position. The shape of the burst light curve was typical for SGR bursts, but with an unusually long duration. There was a short weak precursor ~0.3 sec long at T0-0.4 sec, followed by a 0.1 sec rise and a 22 sec decay. There was a weaker short soft burst at T-T0 ~110 sec. As observed by Konus-Wind the burst had a fluence (1.53+/-0.02)x10^-4 erg/cm2, and a peak flux on 16-ms time scale (3.50 � 0.16)x10^-5 erg/cm2/sec (both in the 20-200 keV range). The time-integrated spectrum of the burst can be fit by the OTTB spectral model: dN/dE ~ E^{-1} exp(-E/kT) with kT = 19.9 + 0.5 keV, which is typical for SGR 1806-20. All the quoted errors are at 90% c.l. This is the longest SGR burst ever triggered the Konus-Wind. Despite its long duration there is apparently no periodicity in the light curve. The Konus-Wind light curve of this GRB can be seen at http://www.ioffe.rssi.ru/LEA/SGRs/051203_T42203/ Likely, the two previous unusually long SGR-like events detected by the Konus-Wind (Golenetskii et al., GCN 4310) originated from this SGR (both these events were not observed by the Swift-BAT because the SGR 1806-20 was below the horizon). BAT has since observed two short (~0.1 sec) bursts from SGR 1806-20, similar to many bursts seen earlier this year. Note, that the ~40-s long burst from SGR 1900+14 was detected on April 18, 2001 by BeppoSAX, and the Konus-Wind in the waiting mode (Guidorzi et al., 2004, A&A, 416, 297 and references therein). That event was strongly modulated with a 5-s period, but had the comparable fluence and peak flux.