GRB 160314B

G. Vianello (Stanford), J. Racusin (NASA/GSFC), D. Kocevski (NASA/GSFC), F. Longo (University of 
Trieste and INFN), and B. Ahlgren (KTH), report on behalf of the Fermi-LAT team:

At 22:17:53.73 on March 14, 2016 Fermi-LAT detected high-energy emission from GRB 160314B, which 
was also detected by Fermi-GBM (trigger 479686676 / 160314929). 

The best LAT on-ground location is found to be:
RA, Dec (J2000) = 167.56, 45.67 
with an error radius of 0.65 deg (90 % containment, statistical error only). 

Unfortunately, the LAT was not taking data at the trigger time T0, because Fermi was just exiting the South 
Atlantic Anomaly (SAA).  Note that LAT and GBM have slightly different SAA definitions in onboard software.  
However, LAT resumed data taking ~30 seconds after T0, and the GRB was 21 deg from the LAT boresight 
at that time. 

The LAT data show a significant increase in the event rate that is spatially and temporally 
correlated with the trigger with high significance. The highest-energy photon is a 900 MeV event which is 
observed ~630 seconds after the GBM trigger.

The Fermi-LAT point of contact for this burst is B. Ahlgren (bjornah@kth.se).

The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater 
than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and 
many scientific institutions across France, Italy, Japan and Sweden.

C. M. Hui (NASA/MSFC) report on behalf of the Fermi GBM Team:

At 22:17:53.73 UT on 14 March 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 160314B (trigger 479686677 / 160314929),
which was also detected by the LAT (G. Vianello et al., GCN 19197
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 ). 
GBM triggered on this GRB ~70s after exiting the SAA. 
The GBM on-ground location is consistent with the LAT position.

The angle from the Fermi LAT boresight at the GBM trigger time 
is 21 degrees.

The GBM light curve shows two peaks with a duration (T90) 
of about 100 s (50-300 keV). The time-averaged spectrum 
from T0-5.6 s to T0+18.9 s is best fit by a power law function 
with an exponential high-energy cutoff.  The power law index 
is -1.19 +/- 0.05 and the cutoff energy, parameterized as Epeak, 
is 954.5 +/- 274.0 keV.

The event fluence (10-1000 keV) in this time interval is
(8.98 +/- 0.34)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+8.4 s in the 8-1000 keV band
is 3.25 +/- 0.24 ph/s/cm^2.

A Band function fits the spectrum equally well with
Epeak = 848.9 +/- 368.0 keV, alpha = -1.20 +/- 0.06,
and beta = -1.86 +/- 0.22.

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