GRB 161020B

K. Hurley, on behalf of the IPN,

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

A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, D. Svinkin,
and T. Cline on behalf of the Konus-Wind team,

V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa,
and A. Goldstein, on behalf of the Fermi GBM team,

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

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team, and

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

A long-duration GRB 161020B has been detected by Fermi (GBM),
Konus-Wind, INTEGRAL (SPI-ACS), Mars-Odyssey (HEND), and Swift (BAT)
at about 65597 s UT (18:13:17). The burst was outside the coded
field of view of the BAT.

We have triangulated it to a preliminary, 3 sigma error box whose
coordinates are:
---------------------------------------------
  RA(2000), deg                 Dec(2000), deg
 ---------------------------------------------
 Center:
   63.105 (04h 12m 25s) -75.580 (-75d 34' 49")
 Corners:
   68.180 (04h 32m 43s) -76.773 (-76d 46' 23")
   68.921 (04h 35m 41s) -76.461 (-76d 27' 38")
   58.787 (03h 55m 09s) -74.305 (-74d 18' 18")
   57.959 (03h 51m 50s) -74.583 (-74d 35' 00")
 ---------------------------------------------
The error box area is 4250 sq. arcmin, and its maximum
dimension is 3.4 deg (the minimum one is 21 arcmin).
The Sun distance was about 90 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB161020_T65597/IPN/

The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.

A.Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 161020B
(IPN triangulation: Hurley et al., GCN Circ. 20091
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triggered Konus-Wind at T0=65597.4 s UT (18:13:17.400).

The burst light curve shows a multipeaked structure
started at ~T0-9 s with a total duration of ~45.6 s.
The emission is seen up to 3 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB161020_T65597/

As observed by Konus-Wind, the burst
had a fluence of 5.12(-0.48,+0.54)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+3.136 s,
of 6.42(-1.29,+1.33)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+37.888 s)
is best fit in the 20 keV - 3 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -1.03(-0.10,+0.11),
the high energy photon index beta = -2.63(-0.59,+0.26),
the peak energy Ep = 186(-19,+21) keV
(chi2 = 69/64 dof)

The spectrum near the maximum count rate
(measured from T0+0.256 to T0+5.120 s)
is best fit in the 20 keV - 3 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.51(-0.10,+0.11),
the high energy photon index beta = -2.72(-0.32,+0.21),
the peak energy Ep = 224(-16,+17) keV
(chi2 = 58/61 dof)

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