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GRB 110808B

GCN Circular 12269

Subject
IPN triangulation of GRB 110808B (short/hard/intense)
Date
2011-08-10T21:29:44Z (14 years ago)
From
Kevin Hurley at UCBerkeley/SSL <khurley@ssl.berkeley.edu>
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.

GCN Circular 12271

Subject
Konus-Wind observation of GRB 110808B
Date
2011-08-11T11:15:57Z (14 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
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)
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.

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