GRB 060806

K. Hurley and T. Cline, on behalf of the Ulysses, Mars Odyssey,
and Konus GRB teams,

I. Mitrofanov, A. Kozyrev, M. Litvak, A. Sanin, V. Tret'yakov and A.
Parshukov, on behalf of the HEND-Odyssey GRB team,

W. Boynton, C. Fellows, K. Harshman, C. Shinohara and R. Starr, on
behalf of the GRS-Odyssey GRB team,

S. Golenetskii, E. Mazets, V. Pal'shin, and D. Frederiks on behalf of
the Konus-Wind team,

D. M. Smith, R. P. Lin, J. McTiernan, R. Schwartz, C. Wigger, W.
Hajdas, and A. Zehnder, on behalf of the RHESSI GRB team, 

K.Yamaoka, M.Ohno, Y.Fukazawa, T.Takahashi, M.Tashiro, Y. Terada,
T.Murakami, and K.Makishima on behalf of the Suzaku WAM team, and

S. Barthelmy, J. Cummings, N. Gehrels, and H. Krimm, on behalf of
the Swift-BAT team,

report:

This burst was observed by Ulysses, Mars Odyssey, Konus, RHESSI,
Suzaku, and Swift-BAT (outside the field of view) at 51821 s.  It was
long (~120 s) and exceptionally bright (details of the spectrum will be
given in a forthcoming GCN Circular).  We have triangulated it to an ~
8 sq. arcmin. error box (3 sigma) whose coordinates are:

    RA(2000)                 DEC(2000)
 18 h  8 m 34.56 s    -20 o 22 '  49.51 "  (CENTER)
 18 h  8 m 34.80 s    -20 o 24 '   9.69 "  (CORNER)
 18 h  8 m 47.14 s    -20 o 24 '  45.83 "  (CORNER)
 18 h  8 m 22.00 s    -20 o 20 '  53.12 "  (CORNER)
 18 h  8 m 34.32 s    -20 o 21 '  29.33 "  (CORNER)

This error box may be improved.

K. Hurley, S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, D. M.
Smith, R. P. Lin, J. McTiernan, R. Schwartz, C. Wigger, W.  Hajdas, A.
Zehnder, K.Yamaoka, M.Ohno, Y.Fukazawa, T.Takahashi, M.Tashiro, Y.
Terada, T.Murakami, K.Makishima, S. Golenetskii, E. Mazets, V.
Pal'shin, and D. Frederiks, report:

The position of GRB060806 (Hurley et al. GCN 5416
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 ) is consistent
with that of SGR1806-20, and the spectrum of this burst is soft.
Therefore the origin of this event is almost certainly SGR1806-20,
which has been active recently.  This type of bursting behavior
appears to be unique, however, so observations at other wavelengths are
encouraged.

S.Golenetskii, D.Frederiks, V.Pal'shin, R.Aptekar, T.Cline
and E.Mazets on behalf of the Konus-Wind team report:


The soft gamma-ray event 060806 related to SGR1806-20
(Hurley et al., GCN 5416
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 , 5419
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 ) is of great interest,
However it hardly can be defined as unique for SGR1806-20,
all of the main features of this event were also observed earlier.
In 2006 SGR1806-20 renewed its activity in the middle of July.
Until now it has emitted about 20 soft bursts.

Date     UT, s           Instrument/Spacecraft
                     Konus-Wind    Konus-A (Cosmos-2421)
060717   50457          yes              yes
060717   57178          yes              no
060718   11636          yes              no
640718   64171          no               yes
060718   69585          yes              yes
060721   61862          yes              no
060728   30102          no               yes
060729   76209          yes              no
060731   27269          yes              yes
060806   21037          yes              yes
060806   51824          yes              no
060807    3806          yes              no
060807    5881          yes              yes
060807   34982          yes              no
060807   83305          yes              no
060808   16377          yes              no


The GRB060806 composes a cluster of 6 separate bursts
similar to clusters observed in 2004 on October 5, December 24 and 25.
Energy spectra of all bursts in the table are identical,
revealing the same value of kT = 20 +/- 0.5 keV.
What is more, the last burst in the cluster, wich lasts for
~30 s and exhibits three broad pulses separated by
time intervals of ~7.55 s, strikingly resembles the light curve
of the soft burst from SGR 1806-20 occured on December 3, 2005.
This burst also starts a quick growing spike followed by
a long tail with two broad if less pronounced peaks of periodic pulsations.


Date     Duration     Fluence          Fmax           kT
             sec       erg cm-2     erg cm-2 s-1       keV

060806     30.8        2.4x10-4      4.7x10-5         20
051203     22          1.6x10-4      3.4x10-5         20

A comparative chart of the two events lightcurves one can find at:
http://www.ioffe.ru/LEA/SGR/060806/0806-060806-051203.jpg