GCN Circular 4946
Subject
Konus-Wind observation of the recent SGR 1900+14 activity. Will
Date
2006-04-03T15:03:04Z (20 years ago)
From
Valentin Pal'shin at Ioffe Inst <val@mail.ioffe.ru>
S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks and
T. Cline on behalf of the Konus-Wind team, report:
Konus-Wind triggered twice on March 29 due to SGR 1900+14 activity.
The first trigger occurred at 5282.959 s UT (01:28:02.959).
This burst was detected and located by Swift BAT (Moretti et al., GCN
4933). It was an ordinary single spike SGR burst with a duration of
~0.07 sec. It had a fluence 7.21(-1.46,+0.91)x10^-7 erg/cm2 (in the
20-200 keV range). Its spectrum is well fitted by OTTB model with
kT=18.3(-3.1,+3.7) keV. All the quoted errors are at the 90% confidence
level.
Much more interesting event triggered Konus-Wind at T0=9928.369 s UT
(02:45:28.369). It was a series of bursts. The trigger part of the
series contains seven intense bursts and several substantially weaker
bursts. The fluences of the intense bursts vary from ~10^-7 to
1.5x10^-6 erg/cm2 (in the 20-200 keV range).
At this time Swift was in SAA and did not detect these bursts.
After the end of the Konus-Wind trigger record and during data
read-out much more intense cluster of the bursts (observed and located
by Swift-BAT (Romano et al., GCN 4934) was detected by Konus-Wind at
T-T0=458 s (02:53:08) with coarse time resolution of 3.96 sec.
As observed by Konus-Wind the cluster had a duration of ~25 sec.
Fortunately, the multichannel spectra were accumulated by Konus-Wind
during this cluster of bursts.
We conservatively estimate the cluster fluence to be
(1-2)10^-4 erg/cm2 (in the 20-200 keV range).
This value can be refined.
It is worth to notice that the reactivation of SGR 1900+14 in 1998
started with several single bursts, which were shortly followed by a
series of bursts on 1998 May 30.
(http://www.ioffe.rssi.ru/LEA/SGR/Catalog/Data/1900/980530a.htm ;
Aptekar et al., ApJSS, 137, 227 (2001))
This series occurred 89 days before the 27 August 1998 giant flare.
The first burst series from SGR 1806-20 was detected on 2004 October 5
by INTEGRAL-IBIS/ISGRI (Mereghetti et al., GCN 2763;
Gotz, Mereghetti, and Mirabel, GCN 2764)
and Konus-Wind (Golenetskii et al., GCN 2769),
83 days before the 27 December 2004 giant flare from this SGR.
Other two series from SGR 1806-20 were detected by Konus-Wind on 2004
December 21 and 25.
The March 29 series, considered here, resembles the burst series
mentioned above, and has several times greater fluence.
We conclude that at present time SGR 1900+14 demonstrates a behavior
similar to pre-giant flare state. So we may expect a further increase
activity of SGR 1900+14 and a repeated (!) giant flare from this SGR at
the latter half of June.