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GCN Circular 2831

Subject
Summary of the recent bursts from SGR 1806-20
Date
2004-11-04T14:12:33Z (20 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks
on behalf of Konus-Wind and Helicon/Coronas-F teams,

T. Cline on behalf of the Konus-Wind team, and

A. Rau, A. von Kienlin, G. Lichti on behalf of the INTEGRAL SPI-ACS
GRB team report:


SGR 1806-20 remains in the active state. Since the last SGR burst
041017, listed in GCN 2823, Konus-Wind and Helicon-Coronas-F have
detected seven SGR-like bursts in the trigger mode. Two of them were
also detected by INTEGRAL SPI-ACS.

The most recent intense SGR burst was detected by Helicon-Coronas-F
today (041104) at 04:17:08.929 UT. Konus-Wind data aren't available
yet.

The following table summarizes the bursts:

Date      Time,    Instr*  Duration,   Fluence,     Peak Flux,   kT**
           s UT                s      (20-200 keV)  (20-200 keV)  keV
                                       ergs/cm2      ergs/cm2 s
-----------------------------------------------------------------------
041026    76305.409  K     0.54      3.0E-6        2.4E-5     21.4+/-1.2

041027    35196.737  K     0.55      5.0E-6        2.6E-5     18.6+/-1.1

041029    22099.384  K     0.16      2.5e-6        3.4E-5     17.7+/-1.3

041031(a) 57535.834  H     0.056     4.7e-7        1.2e-5     17.8+/-1.6

041031    61900.552  K, I  0.70      1.2e-5        4.4e-5     18.9+/-0.6

041102(b) 26875.713  K     0.19      1.1e-5        9.9e-5     22.6+/-1.2

041104(c) 15428.929  H, I  1.6       1.9e-5        2.0e-5     21.8+/-0.5
------------------------------------------------------------------------
*  -   the intrument, which detected the burst:
        K   = Konus-Wind
        H   = Helicon-Coronas-F
        I   = INTEGRAL SPI-ACS

**  -  the last column contains the values of spectral parameter kT
        for the OTTB spectral model: dN/dE ~ E^{-1} exp(-E/kT)

(a) -  this burst was also observed by Konus-Wind in the
        background mode. Estimated time delay is consistent with
        SGR 1806-20 position.
(b) -  this burst was also observed by Helicon-Coronas-F in the
        background mode. Estimated time delay is consistent with
        SGR 1806-20 position.
(c) -  We have triangulated it to Coronas-INTEGRAL annulus centered at
        RA(2000) = 225.846 deg, Decl(2000) = 44.432 deg,
        whose radius is 77.4 � 4.0 deg (3 sigma).
        The center line of this annulus passes 0.02 degrees from
        the position of SGR 1806-20.

The Konus-Wind ecliptic latitude response indicates
that the source of the remaining bursts is near ecliptic plane,
so we suppose, that they are also originated from SGR 1806-20.

The peak flux of the burst on 041102 was nearly the same as
the peak flux of the brighest burst  detected by Konus-Wind
from SGR 1806-20 on 040828 (GCN 2693).
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