GRB 070821

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

I.G. Mitrofanov, M.L. Litvak, A.S. Kozyrev, A.B. Sanin and V.I. Tretyakov,
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, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and
T. Cline 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, and

J. Goldsten, on behalf of the MESSENGER NS GRB team,

Konus-Wind, Mars Odyssey (HEND and GRS), RHESSI, and MESSENGER (NS)
observed this burst at 46164 s.  (MESSENGER data downlinks were delayed
because the spacecraft is in conjunction.)  As observed by Konus, it had a
duration ~ 180 s, a 20-2000 keV fluence ~ 10^-4 erg/cm2, and an
Epeak ~ 300 keV.  We have triangulated it to a preliminary, 3
sigma error box whose area is ~ 70 sq. arcmin. and whose coordinates are:


RA(2000) DEC(2000)
95.527   -63.850 DEGREES (CENTER)
95.422   -63.928 DEGREES (CORNER)
95.811   -63.842 DEGREES (CORNER)
95.242   -63.858 DEGREES (CORNER)
95.631   -63.772 DEGREES (CORNER)

This error box may be improved.  Spectral information will follow in
a separate circular.

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

The very bright long GRB 070821 localized by the IPN (Hurley et al.,
GCN 6764
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 ) triggered Konus-Wind at T0=46164.332 s UT (12:49:24.332).

The Konus-Wind light curve shows a soft precursor started at T-T0 ~-6 s 
(with a duration of ~8 s), followed by a very intense multipeaked pulse 
at T-T0 ~120 s and a weaker pulse at T-T0 ~180 s
(there is an emission between these two intense pulses).
The total burst duration is ~215 s.

As observed by Konus-Wind the burst
had a fluence of 1.02(-0.04, +0.03)x10^-4 erg/cm2,
and a 256-ms peak flux measured from T0+126.720 s
of 1.38(-0.11, +0.09)x10^-5 erg/cm2/s
(both in the 20 keV - 2 MeV energy range).

The time-integrated spectrum of the main episode
(from T0+114.944 s to T0+203.776 s) can be fitted
(in the 20 keV - 2 MeV range)
by a power law with exponential cutoff model:
dN/dE ~ E^(-alpha)*exp(-E*(2-alpha)/Ep)
with alpha = 1.299  +/- 0.037
and Ep = 268 (-17, +19) keV (chi2 = 67.8/59 dof).

The spectrum of the most intense pulse
(accumulated from T0+114.944 s to T0+146.432 s)
is well fitted (in the 20 keV - 2 MeV range)
by a power law with exponential cutoff model
with alpha = 1.215  +/- 0.030
and Ep = 289 (-14, +15) keV (chi2 = 68.3/59 dof).
This pulse had a fluence of 8.34(-0.24, +0.17)x10^-5 erg/cm2.

All the quoted errors are at the 90% confidence level.

The Konus-Wind light curve of this GRB is available
at http://www.ioffe.rssi.ru/LEA/GRBs/GRB070821_T46164/