GRB 150118C

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

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,

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

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

The short-duration, hard-spectrum GRB 150118C has been observed by Fermi 
(GBM trigger  443312075), Konus-Wind, and Mars Odyssey (HEND), so far, 
at about 80073 s UT (22:14:33).

We have triangulated it to a preliminary, 3 sigma error box whose
coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   160.077 (10h 40m 18s) -27.555 (-27d 33' 19")
  Corners:
   160.615 (10h 42m 28s) -27.410 (-27d 24' 37")
   160.100 (10h 40m 24s) -27.656 (-27d 39' 22")
   159.542 (10h 38m 10s) -27.693 (-27d 41' 34")
   160.054 (10h 40m 13s) -27.455 (-27d 27' 16")
  ---------------------------------------------
The error box area is 366 sq. arcmin, and its maximum
dimension is 1.0 deg (the minimum one is 12 arcmin). The Sun distance 
was 119 deg.

The center of the GBM ground position is 4.0 deg from the center of the box.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB150118_T80075/IPN/

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

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

The short-duration GRB 150118C
(IPN triangulation: Golenetskii et al., GCN Circ. 17324
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 )
triggered Konus-Wind at T0=80075.206 s UT (22:14:35.206).

The burst light curve shows a single pulse with a duration ~0.1 s.
The emission is seen up to ~1 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150118_T80075/

As observed by Konus-Wind, the burst
had a fluence of 6.2(-1.2,+1.5)x10^-7 erg/cm2,
and a 16-ms peak flux, measured from T0-0.020 s,
of 1.3(-0.4,+0.5)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+0.064 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.91 (-0.44,+0.56)
and Ep = 286 (-94,+204) keV (chi2 = 8/13 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
(chi2 = 8/12 dof)

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

E. Burns (UAH) report on behalf of the Fermi GBM Team:

"At 22:14:32.66 UT on 18 January 2015, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 150118C (trigger 443312075 / 150118927).
The GBM on-ground location is consistent with the IPN location
(K. Hurley et al. 2015, GCN 17324
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 ). The angle from the Fermi LAT
boresight is 92 degrees.

The GBM light curve consists of a single pulse
with a duration (T90) of about 0.3 s (50-300 keV).
The time-averaged spectrum from T0-0.128 s to T0+0.320 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.1 +/- 0.1 and
the cutoff energy, parameterized as Epeak, is 658 +/- 143 keV.
It is equally well fit by a Band function with
Epeak = 415 +/- 117 keV, alpha = -0.9 +/- 0.1, and
beta = -2.0 +/- 0.2.

The event fluence (10-1000 keV) in this time interval is
(1.2 +/- 0.1)E-06 erg/cm^2. The 64-ms peak photon flux measured
starting from T0+0.00 s in the 10-1000 keV band
is 39.6 +/- 2.0 ph/s/cm^2.

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