GRB 110808B

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

I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,

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

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

D. M. Smith, R. P. Lin, J. McTiernan, R. Schwartz, and W.
Hajdas, on behalf of the RHESSI GRB team, report:

GRB 110808B, a very intense short-duration, hard spectrum GRB,
was observed by Konus-Wind, Mars Odyssey, MESSENGER, and RHESSI at
56693 s UT.  We have triangulated it to a preliminary, 3 sigma error
box whose area is about 108 square arcminutes, whose maximum dimension
is ~22 arcminutes, and whose coordinates are:
             RA(2000)                         Dec(2000)
CENTER:   266.1808=17 h 44 m 43.4 s    -37.7463=-37 o 44 '  47 "
CORNERS:  266.0492=17 h 44 m 11.8 s    -37.7586=-37 o 45 '  31 "   
          266.3453=17 h 45 m 22.9 s    -37.8732=-37 o 52 '  24 "     
          266.0166=17 h 44 m 04.0 s    -37.6169=-37 o 37 '  01 "     
          266.3123=17 h 45 m 14.9 s    -37.7332=-37 o 44 '  00 "

Although this error box lies at Galactic latitude -5 degrees, it does
not include any of the known magnetars.  A Swift ToO has been requested.
Further details of the spectrum and time history will appear in a
forthcoming GCN Circular.  A map is posted at
ssl.berkeley.edu/ipn3/110808B.  This error box can be improved.

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

The short-duration extremely hard GRB 110808B
(localized by IPN: Hurley et al., GCN 12269
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triggered Konus-Wind at T0=56695.237s UT (15:44:55.237)

The burst light curve shows a single bright hard pulse,
with a duration of ~0.5 s and much weaker tail of
the emission which is detectable till T0+8 s.
The emission is seen up to 13 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB110808_T56695/

As observed by Konus-Wind the burst
had a fluence of (1.6 � 0.2)x10-5 erg/cm2,
and a 16-ms peak flux, measured from T0+0.112 s,
of (1.1 � 0.2)x10-4 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The spectrum of the burst (measured from T0 to T0+0.256 s)
is best fitted in the 20 keV - 10 MeV range
by a power law with exponential cutoff model, for which
alpha = -1.13 (-0.08, +0.08),
and Ep = 2960(-796, +1217) keV,
chi2 = 53.2/45 dof.
Fitting this spectrum by the GRB (Band) function yields
the following model parameters:
the low-energy photon index alpha = -1.13 (-0.08, +0.07),
the high energy photon index beta = -2.5 (<-1.9),
the peak energy Ep = 2630(-744, +836) keV,
chi2 = 54.3/44 dof.

The spectrum at the maximum count rate
(measured from T0+0.064 to T0+0.128 s)
is best fitted in the 20 keV - 10 MeV range
by a power law with exponential cutoff model, for which
alpha = -1.07 (-0.11, +0.12),
and Ep = 4238(-1530, +3270) keV,
chi2 = 12.5/16 dof.

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