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GCN Circular 2665

Subject
Increase of SGR 1806-20 activity
Date
2004-08-26T15:19:46Z (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:


Recently the increase of bursting activity from SGR 1806-20
was detected by Konus-Wind, INTEGRAL SPI-ACS, and Helicon-Coronas-F.

Konus-Wind has detected 7 bursts in the trigger mode and 5 bursts
in the background mode.
Additional SGR-like burst was detected by Helicon-Coronas-F in
the background mode and triggered INTEGRAL SPI-ACS
(the burst was missed by Konus-Wind due to data read out).

The most recent burst detected on August 25 at 85512.611 s UT
is the brightest burst ever observed by Konus-Wind from SGR 1806-20.

The following table summarizes the bursts:


Date     Time*,     Duration,   Fluence,       Peak Flux,  Observed by**
           s UT          s      (20-200 keV)   (20-200 keV)
                                ergs/cm2       ergs/cm2 s
-----------------------------------------------------------------------
040814   45466.575  0.18         1.6E-6        2.1E-5       K(tr)

040819   22636.891  0.80         1.4E-5        2.5E-5       K(tr)

040820   71208.277  0.06         9.4E-7        3.1E-5       K(tr)

040821   35217      <3           1.7E-6          -          K(bg), I

040821   61297.013  0.22         2.5E-6        2.0E-5       K(tr), I

040822    9646      <3           5.0E-7          -          K(bg)

040823   22462      <3           8.0E-7          -          K(bg)

040823   36755      <3           5.0E-7          -          K(bg)

040823   40994.643  0.14         1.5E-6        4.5E-5       K(tr)

040823   48073.891  0.70         1.0E-5        4.2E-5   K(tr), I, H(bg)

040823   48363      <2           3.2E-6          -          I, H(bg)

040823   58681      <3           6.0E-7          -          K(bg)

040825   85512.611  1.10         2.1E-5        7.0E-5       K(tr), I
------------------------------------------------------------------------
*  - Konus-Wind (or Helicon) time is given
** - the last column contains the s/c which observed this burst:
     K - Konus-Wind, I - INTEGRAL SPI-ACS,
     H - Helicon-Coronas-F. For Konus and Helicon in the brackets
     the observation mode is given: tr - trigger, bg - background.


The Konus-INTEGRAL annuli for 3 bursts are:

  Date   Time,          Center           Radius
         s UT        RA       DEC   and its uncertainty (3sigma)
		    deg      deg	 deg						
----------------------------------------------------
040821  61297.013  310.141 -16.864   35.724+/-0.678

040823  48073.891  311.668 -14.712   37.647+/-0.762

040825  85512.611  314.503 -14.941   40.588+/-0.454


Because all these annuli pass through the position of SGR 1806-20,
we believe that it is the source of these events.

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