//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2896 SUBJECT: Very high activity of SGR 1806-20 DATE: 04/12/22 16:57:06 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks and T. Cline on behalf of the Konus-Wind team, report: During 21 December more than 30 SGR-like bursts were detected by Konus-Wind and Helicon-Coronas-F with peak fluxes varied from 5e-7 to 8e-5 erg /cm2 s. The time interval between bursts varied from seconds to hours. The triangulation of several these bursts indicated that their origin is SGR 1806-20. This is the second series of bursts from this source. The previous one was detected on 5 October (GCN 2769). Now we have the data till 01:28 UT December 22. The last burst is seen at 00:50:52 s UT in the Helicon background data. Details on triangulation and the full list of bursts with their characteristics will be given later. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2920 SUBJECT: Giant flare from SGR 1806-20 detected by INTEGRAL DATE: 04/12/29 11:19:07 GMT FROM: Sandro Mereghetti at IASF/CNR J.Borkowski (CAMK, Torun), D. Gotz, S. Mereghetti (IASF, Milano), N.Mowlavi, S.Shaw, M.Turler (ISDC, Versoix), report: A large flare most likely coming from the soft repeater SGR 1806-20 has been detected with INTEGRAL on December 27 at 21:30:26 UT. The flare caused a large and rapid increase in the count rate of the SPI ACS which reached a peak flux of 2x10^6 counts/s (compared to a background level of 88,000 counts/s ). The initial spike, lasting about 1.5 s, is followed by a 300 s long tail in which pulsations at 7.57 s are clearly visible. The IBAS ACS system triggered on a fainter event occurring about 140 s before the main flare and possibly due to a precursor from the same source. No positional information is available with the SPI ACS data. The shape of the light curve, similar to that of the 27 August 1998 flare from SGR 1900+14, but with a periodicity of 7.6 s, indicates that SGR 1806-20 is the most likely origin of the observed event. This would be the first giant flare observed from SGR 1806-20. At the time of the flare, INTEGRAL was pointing at 106 degrees from the direction of SGR 1806-20, which was outside the fields of view of the imaging instruments. See also the News section of http://ibas.mi.iasf.cnr.it/ for further details of the ongoing analysis This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2921 SUBJECT: IPN localization of giant flare from SGR1806-20 DATE: 04/12/29 12:30:42 GMT FROM: Kevin Hurley at UCBerkeley/SSL K. Hurley and T. Cline, on behalf of the Ulysses and Mars Odyssey GRB teams, I. Mitrofanov, S. Charyshnikov, V. Grinkov, A. Kozyrev, M. Litvak, and A. Sanin, on behalf of the HEND-Odyssey GRB team, and W. Boynton, C. Fellows, K. Harshman, C. Shinohara and R. Starr, on behalf of the GRS-Odyssey GRB team, report: The giant flare observed by INTEGRAL (SPI-ACS - GCN 2920) was also detected by Mars Odyssey (GRS). Data from other IPN spacecraft have not been received yet. A very preliminary analysis indicates that the arrival time at Odyssey is indeed consistent with an arrival direction from SGR1806-20. Further analysis is underway and will be reported later. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2922 SUBJECT: The giant outburst from SGR 1806-20 DATE: 04/12/29 13:18:07 GMT FROM: Dmitry Frederiks at Ioffe Institute E. Mazets, S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, and T. Cline on behalf of the Konus-Wind team, report: On December 27, 2004, the Konus-Wind instrument detected a giant flare from SGR 1806-20. The flare was preceded by a high emission of recurrent soft bursts. A series of numerous bursts occurred on October 5. On the analogy of the behaviour of SGR 1900+14 before the giant flare on 1998 August 27, it was possible to expect, that SGR 1806-20 is close to generation of a giant flare (GCN 2769). Another series began on December 21 and lasted until the giant flare. These bursts were strong in their flux, exhibiting a well pronounced spectral variability and in some cases unusual spectral features. A record of the giant outburst was triggered by a recurrent burst, which was the strongest in the series. The giant outburst occurred on 142 s after this trigger. The flare started with a very intense initial pulse, resulting in overloading of the detector. It was followed by a long pulsating tail lasted more than 380 s. A measured period of the pulsations is 7.57 ± 0.07 s, indicating its increasing since 2000, when value of 7.49 s was determined in Chandra observations of X-ray persistent flux (Kaplan et al., 2002, ApJ, 564, 935) . Giant outbursts were observed earlier in SGR 0526-66 on 1979 March 5, in SGR 1627-41 on 1998 June 18, in SGR 1900+14 on 1998 August 27. The event of December 27 completes this list for all of well known SGRs. After the outburst, SGR 1806-20 continues to emit recurrent bursts. A determination of energetic and spectral parameters of the outburst will take some time because of a huge intensity of the initial pulse. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2923 SUBJECT: Detection of the SGR 1806-20 giant outburst back-scattered by the DATE: 04/12/29 19:32:36 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks on behalf of Konus-Wind and Helicon/Coronas-F teams, and T. Cline on behalf of the Konus-Wind team report: We present an evidence of Helicon-Coronas-F detection of the giant outburst from SGR1806-20 which was scattered back from the Moon. At the time of the outburst SGR1806-20 was occulted by the Earth for Coronas-F. A short burst triggered Helicon at 21:30:29.303s UT on Dec 27. A time delay between Konus-Wind and Helicon-Coronas-F detections is -7.70 s. This value corresponds exactly to burst travelling time from the Wind to the Moon and back to the Coronas-F. The spectrum of the event detected by the Helicon is highly unusual. It looks like a broad assymetric line peaked at ~100 keV. Apparently such a shape corresponds to back-scattering peak of a huge initial pulse of the outburst. The fluence of event is about 7.5x10^-7 erg cm-2 in 25-400 keV range. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2925 SUBJECT: SGR1806-20: Swift-BAT observation of the 041227 super-flare DATE: 04/12/30 19:31:47 GMT FROM: David Palmer at LANL D. Palmer (LANL), S. Barthelmy, L. Barbier (GSFC), S. Campana (OAB), J. Cummings (GSFC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (GSFC/UMD), K. Hurley (UCB), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), K. McLean (LANL), T. Sakamoto (GSFC), G. Sato (ISAS), M. Suzuki (Saitama), M. Tashiro (Saitama), J. Tueller (GSFC) on behalf of the Swift-BAT team: The Burst Alert Telescope (BAT) on Swift triggered on and recorded the super-flare outburst of SGR1806-20 at 21:30:26 2004-12-27. We did not localize the burst because it was outside the coded aperture FOV of the instrument. The angle from the bore sight was 105 degrees, illuminating the instrument from slightly underneath the plane of the detectors through the XRT and UVOT instruments and the body of the spacecraft. Even with the absorption from this material, the main peak countrate in the detector array is saturated at 2.5E6 evts/sec (the maximum count rate the detector electronics is capable of). The FWHM of the main peak was ~0.5 sec. After the main peak, BAT recorded a series of 51 pulsations with a period of 7.56 sec and with three peaks within each pulsation. Prior to the super-flare peak, there was a precursor peak at T-143 sec, The peak count rate (well below the BAT instrumental saturation level) was 31,000 evts/sec (15-350 keV, with nearly all counts below 100 keV) and with a square profile of rise and fall times less than 100 msec and width of 1.2 sec. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2927 SUBJECT: SGR1806-20: RXTE-PCA observation of the 041227 super-flare DATE: 05/01/02 20:10:02 GMT FROM: Craig Markwardt at NASA/GSFC/UMD E. Smith (GSFC/L3), J. Swank(GSFC), C. Markwardt(GSFC/UMD), Y. Rephaeli(UCSD/TAU), D. Gruber(Eureka), M. Persic(Obs.Ast.Trieste), and R. Rothschild (UCSD) The Proportional Counter Array (PCA) on the Rossi X-Ray Timing Explorer (RXTE) detected the precursor and the main flares of SGR 1806-20 on 2004-12-27 (Borkowski et al., GCN #2920). The times of the flares were 21:28:03.5 and 21:30:26.6 UTC, respectively, which agree with the arrival times reported by the Swift-BAT Team (Palmer et al., GCN #2925). Two of the All Sky Monitor detectors were turned off by the high rates. HEXTE detected only the initial 1 s spike of the main flare. The SGR was 31 degrees off the boresight of the 1.1 degree shielded copper collimators of the PCA and the lead collimators of HEXTE. As seen by the PCA, the precursor lasted approximately 1.2 s. After an initial pulse of the main flare, the flux was pulsed at a period of 7.579 +/- 0.002 s (non-barycentered). The PCA observed 3 peaks in the pulses, as did the BAT, during an interval of approximately 360 s. Three PCA detectors were on and recorded peak count rates of 17-25 kct/s (0.125 s bins). However, the detectors were probably saturated during the initial peak of the main flare. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2928 SUBJECT: VLA observations of SGR 1806-20 DATE: 05/01/03 20:27:48 GMT FROM: Patrick B. Cameron at Caltech P. B. Cameron (Caltech) and S. R. Kulkarni (Caltech) report: "We observed the position of SGR 1806-20 with the Very Large Array (VLA) in A-configuration on 2005 Jan 3.81 UT (t ~ 6.9 days after the giant flare, GCN #2920). We detect a radio source coincident with the X-ray position reported by Kaplan et al. (2002, ApJ, 564, 935) at the approximate freqeucnies and flux densities listed below. Freq (GHz) Flux density (mJy) -------------------------------- 4.86 73 8.46 41 This is a factor of brighter of 100 times brighter at 8.46 GHz than SGR 1900+14 at peak. Further observations are planned. The National Radio Astronomy Observatory is operated by Associated Universities, Inc., under cooperative agreement with the National Science Foundation." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2929 SUBJECT: SGR1806 VLA Observations DATE: 05/01/03 20:43:51 GMT FROM: Chryssa Kouveliotou at MSFC RADIO DETECTION OF SGR 1806-20 FOLLOWING A GIANT FLARE B. M. Gaensler (CfA), C. Kouveliotou (NASA/MSFC, NSSTC), R. Wijers (University of Amsterdam), M. Garrett (JIVE), M. Finger, P. Woods, S. Patel (USRA, NSSTC), M. McLaughlin (Jodrell Bank) report on behalf of a larger team: We observed the soft gamma-ray repeater SGR 1806-20 with the Very Large Array, approximately 7 days after the detection of a Giant Flare from the source (Borkowski, J. et al., 2004, GCN # 2920), on January 3, 2005 for one hour (19:46-20:46 UT). At frequencies of 1.4, 4.9 and 8.5 GHz, we detect an unresolved radio source at coordinates (J2000) RA 18h08m39.3s, Dec -20o24'39.7", with an approximate uncertainty of 0.1" in each coordinate. This is consistent with the X-ray position of SGR 1806-20 as given by Kaplan et al., ApJ 564, 935 (2002). Since this is the first time the source has been observed in radio, we suggest that we detected transient emission from a synchrotron wind bubble, as was seen by Frail et al., Nature, 398, 127 (1999) one to two weeks after a Giant Flare from SGR 1900+14. The preliminary flux density of the source is 160 +/-10, 78 +/-3 and 45 +/-3, mJy at 1.4, 4.9 and 8.5 GHz, respectively. Further observations are planned with the VLA on January 4, 14:15-15:15 UT. We are grateful to the VLA Scheduling Officers (Jim Ulvestadt and Joan Wrobel) for approving our request for Target of Opportunity observations of the source. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2930 SUBJECT: VLA observations of SGR 1806-20 DATE: 05/01/03 21:00:02 GMT FROM: Patrick B. Cameron at Caltech P. B. Cameron (Caltech) and S. R. Kulkarni (Caltech) report: "We observed the position of SGR 1806-20 with the Very Large Array (VLA) in A-configuration on 2005 Jan 3.81 UT (t ~ 6.9 days after the giant flare, GCN #2920). We detect a radio source coincident with the X-ray position reported by Kaplan et al. (2002, ApJ, 564, 935) at the approximate freqeucnies and flux densities listed below. Freq (GHz) Flux density (mJy) -------------------------------- 1.43 164 Further observations are planned. The National Radio Astronomy Observatory is operated by Associated Universities, Inc., under cooperative agreement with the National Science Foundation." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2931 SUBJECT: DETECTION OF POLARIZATION OF THE RADIO EMISSION FROM SGR 1806-20 DATE: 05/01/03 21:16:21 GMT FROM: Peter Woods at UAH/MSFC DETECTION OF POLARIZATION OF THE RADIO EMISSION FROM SGR 1806-20 B. M. Gaensler (CfA), C. Kouveliotou (NASA/MSFC, NSSTC), R. Wijers (University of Amsterdam), M. Garrett (JIVE), M. Finger, P. Woods, S. Patel (USRA, NSSTC), M. McLaughlin (Jodrell Bank) report on behalf of a larger team: Further to the reports on the radio emission from SGR 1806-20 (Cameron & Kulkarni, GCN 2928, and Gaensler et al, GCN 2929, Atel # 373) we detect linear polarization from the source at 1.4, 4.9, 8.5 GHz at a level of at least 2.6, 0.9, 3.8%, respectively. We caution, however, that these are very preliminary results and more detailed analysis is underway to account for the possibility of polarization leakage from the total intensity signal. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2936 SUBJECT: SGR 1806-20, RHESSI observations of the 041227 giant flare DATE: 05/01/05 18:54:11 GMT FROM: Steven E. Boggs at UCB/SSL S. Boggs (UCB), K. Hurley (UCB), D.M. Smith (UCSC), R.P. Lin (UCB), G. Hurford (UCB), W. Hajdas (PSI), C. Wigger (PSI) RHESSI observed both the precursor and the giant flare from SGR 1806-20 in their entirety, staring at 21:28:03.44 UT and 21:30:26.65 UT 2004-12-27 respectively. The SGR was 5 degrees from RHESSI's pointing axis which was directed toward the Sun. This placed the SGR outside the normal imaging FOV of the instrument. During the main peak of the flare the RHESSI spectroscopy detectors were saturated for ~0.5s after the rise, but observed the decay of the main peak and the 400-s long oscillatory component. While the main RHESSI spectroscopy detectors (9 segmented germanium detectors operating from 3 keV to 15 MeV) were saturated during the peak, the RHESSI particle detector (used for detecting SAA passages) was able to measure the incident flux with 0.125-s time resolution in two energy channels determined by thresholds in the electronics: >65 keV, and >650 keV. These data indicate significant emission above 650 keV for ~0.25 s, during the giant flare, and softening of the giant peak during its evolution. In addition, even though the RHESSI spectroscopy detectors are saturated during the giant peak, we can use the reset rates of the preamplifiers to constrain the rise and fall times of the giant peak to <1 ms and ~65 ms respectively. The particle detector data and the spectroscopy detector reset rates allow us to set conservative lower limits to the total fluence of the primary giant peak: >0.1 erg/cm^2 and >0.3 erg/cm^2 respectively. This fluence is >1-2 orders of magnitude higher than the 1998 flare of SGR 1900+14, which had a fluence of 7e-3 erg/cm^2 (Hurley et al., Nature 397, 41, 1999). Assuming a distance of ~15 kpc for SGR 1806-20 (Corbel & Eikenberry, A&A 419, 191,2004) and isotropic emission, we derive a lower limit on the total hard X-ray/gamma-ray energy released in the giant peak to be >8e45 erg. We note that given BATSE's sensitivity of <1e-8 erg/cm^2, this type of giant flare would have been detectable by BATSE (as a short, hard GRB) out to >80 Mpc. When they came out of saturation during the giant peak, the RHESSI spectroscopy detectors were measuring a peak count rate of ~280,000 cnt/s. After the giant peak, RHESSI recorded a series of 51 pulsations with a period of 7.56 s, similar to the INTEGRAL, KONUS, and Swift-BAT observations (Borkowski et al., GCN 2920; Mazets et al., GCN 2922; Palmer et al., GCN #2925). The pulse profile shows evidence for both spectral variations throughout the pulse, and evolution of the pulse shapes throughout the decay. The average 20-100 keV pulse profile shows 3-4 peaks in its structure. During this decay phase, the average 20-100 keV flux is well modeled by the trapped fireball model of Thompson & Duncan (ApJ 561, 980, 2001), with an evaporation time t_evap=382 s, and index a=0.606, where flux ~ (1-t/t_evap)^(a/1-a). Preliminary lightcurves show indications of significant spectral softening during the 400-s oscillatory decay. RHESSI observed the precursor during 21:28:03.44-21:28:04.49 UT, with a peak count rate in the spectroscopy detectors of ~30,000 cnt/s, and ~25,000 counts total. The profile is square, as reported by Swift-BAT (Palmer et al., GCN #2925), with emission extending up to 150 keV. We see a rise time for the precursor <50 ms, and a fall time <100 ms. Results of this analysis will be posted as they come available at: http://www.ssl.berkeley.edu/ipn3/041227