GRB 171216B

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,

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

The long-duration GRB 171216B was detected
by Konus-Wind, INTEGRAL (SPI-ACS), CALET (CGBM), and
Mars-Odyssey (HEND) at about 51947 s UT (14:25:47).

We have triangulated it to a preliminary, 3 sigma error box whose 
coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   340.068 (22h 40m 16s) +52.048 (+52d 02' 54")
  Corners:
   340.072 (22h 40m 17s) +51.848 (+51d 50' 54")
   339.877 (22h 39m 30s) +51.992 (+51d 59' 32")
   340.064 (22h 40m 15s) +52.248 (+52d 14' 54")
   340.259 (22h 41m 02s) +52.104 (+52d 06' 15")
  ---------------------------------------------
The error box area is 170 sq. arcmin, and its maximum
dimension is 24 arcmin (the minimum one is 10.0 arcmin).
The Sun distance was 100 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB171216_T51948/IPN

The time history and spectrum will be given in forthcoming GCN 
Circulars.

V. Pal'shin, A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama,
Y. Yamada, A. Tezuka, S. Matsukawa (AGU), K. Yamaoka (Nagoya U),
S. Nakahira (RIKEN), I. Takahashi (IPMU), Y. Asaoka, S. Ozawa, S. Torii (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), W. Ishizaki (ICRR), M. L. Cherry (LSU),
S. Ricciarini (U of Florence), A. V. Penacchioni, P. S. Marrocchesi (U of Siena)
and the CALET collaboration:

The bright GRB 171216B (INTEGRAL SPI-ACS trigger #7972; Hurley et al.
GCN circ. 22263
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 ) triggered the CALET Gamma-ray Burst Monitor (CGBM) at
14:25:47.14 on 16 December 2017.  The burst signal was seen by the all instruments.

The light curve of the SGM shows several short peaks. The emission starts
at T0, peaks at T+3 sec and ends at T+5 sec.  The T90 duration measured
by the SGM data is 3.5 +- 0.4 sec (40-1000 keV).

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1197469387/

The CALET data used in this analysis are provided by the Waseda CALET Operation
Center located at the Waseda University.

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

The long-duration, hard-spectrum GRB 171216B
(IPN triangulation: Hurley et al., GCN circ. 22263
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 ;
CALET-CGBM detection: Pal'shin et al., GCN circ. 22268
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 )
triggered Konus-Wind at T0=51948.499 s UT (14:25:48.499).

The burst light curve shows a multipeaked structure
which starts at ~T0-0.3 s and has a total duration of ~7.4 s.
The emission is seen up to ~5 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB171216_T51948/

As observed by Konus-Wind, the burst
had a fluence of 1.59(-0.29,+0.37)x10^-5 erg/cm2,
and a 16-ms peak flux, measured from T0+0.034 s,
of 2.32(-1.00,+1.15)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -1.11(-0.11,+0.13)
and Ep = 1341(-412,+673) keV (chi2 = 85/98 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.3
(chi2 = 85/97 dof).

The spectrum near the maximum count rate
(measured from T0 to T0+0.064 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
with  alpha = -0.34(-0.37,+0.52)
and Ep = 994(-372,+539) keV (chi2 = 15/16 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.2
(chi2 = 15/15 dof).

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