GRB 131118A

Andrew C. Collazzi (NASA/ORAU) reports on behalf of the Fermi GBM Team:

"At 22:58:57.47 UT on 18 November 2013, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 131118A (trigger 406508340 / 131118.958). The
on-ground calculated location, using the Fermi GBM trigger data,
is RA = 349.7, Dec = -69.4 (J2000 degrees, equivalent to J2000 23h 18.8m,
-69� 24' ), with a statistical uncertainty of 1.0 degrees (radius, 1-sigma
containment, statistical only; there is additionally a systematic error which
is currently estimated to be 2 to 3 degrees). The angle from the Fermi LAT
boresight is 150 degrees.

Due to the high zenith angle of this burst, there may be higher than normal
systematic errors on this location.  This burst was also observed by Swift-BAT
(ground analysis), Suzaku-WAM, and INTEGRAL/SPI-ACS.

The GBM light curve shows a multi-peaked event with a duration (T90)
of about 85 s (50-300 keV). The 1.024-s peak flux during this interval is
12.5 +/- 0.9 erg/s/cm^2 (10-1000 keV). The time-averaged spectrum
from T0-13.8 to T0+99.8 s is equally well fit to a Comptonized model
with Epeak = 370.5 +/- 10.6, alpha = -0.89 +/- 0.03 and a Band model with
Epeak = 366.8 +/- 12.5, alpha = -0.89 +/- 0.03, and beta = -3.4 +/- 0.6.
Both models yield a fluence (10-1000 keV) in this time interval 
of (9.2 +/- 0.1)E-05 erg/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

IPN Triangulation of GRB 131118A

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

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

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

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

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

and

K. Yamaoka, M. Ohno, Y. Hanabata, Y. Fukazawa, T. Takahashi, M. Tashiro,
Y. Terada, T. Murakami, and K. Makishima on behalf of the Suzaku WAM 
team, report:

The long-duration, intense GRB 131118A (Collazzi, GCN 15503
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 ) has been
observed by Fermi (GBM: trigger 406508340), INTEGRAL (SPI-ACS), Swift 
(BAT), Suzaku (WAM), MESSENGER (GRNS), Mars Odyssey (HEND), and 
Konus-Wind, so far, at about 82737 s UT (22:58:57). The burst was 
outside the coded field of view of the BAT.

We have triangulated it to a 3 sigma error box whose
coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   349.863 (23h 19m 27s) -66.833 (-66d 49' 58")
  Corners:
   350.415 (23h 21m 40s) -66.930 (-66d 55' 47")
   349.800 (23h 19m 12s) -66.926 (-66d 55' 32")
   349.313 (23h 17m 15s) -66.733 (-66d 44' 00")
   349.924 (23h 19m 42s) -66.740 (-66d 44' 23")
  ---------------------------------------------
The error box area is 162 sq. arcmin, and its maximum
dimension is 29 arcmin (the minimum one is 12 arcmin). The Sun distance 
was 81.6 deg.

The center of the GBM ground position (Collazzi, GCN 15503
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 ) is 2.6 deg 
from the center of the box.

Some improvement in this triangulation is possible.

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

The long-duration GRB 131118A
(Fermi GBM detection: Collazzi, GCN 15503
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 ;
IPN triangulation: Hurley at al., GCN 15506
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 )
triggered Konus-Wind at T0=82738.919 s UT (22:58:58.919).

The burst light curve shows multiple partly overlapped pulses
from ~T0 to ~T0+140 s.
The emission is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB131118_T82738/
Note: the waiting mode LCs are corrupted for almost whole
duration of the burst.

As observed by Konus-Wind, the burst
had a fluence of (8.40 � 0.06)x10-5 erg/cm2,
and a 64-ms peak flux, measured from T0+63.296 s,
of (5.1 � 0.5)x10-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum (measured from T0 to T0+139.520 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.88 � 0.05,
the high energy photon index beta = -2.83 � 0.25,
the peak energy Ep = 230 � 11 keV,
chi2 = 97.4/96 dof.

The spectrum near the maximum count rate
(measured from T0+57.600 s to T0+65.792 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.80 � 0.04,
the high energy photon index beta = -2.56 � 0.07,
the peak energy Ep = 286 � 8 keV,
chi2 = 110/97 dof.

All the quoted values are preliminary.

[GCN OPS NOTE(21nov13) The GRB name was corrected to 131118A.]