[vsnet-grb-info 17821] GRB 160408A: Fermi GBM detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19265
SUBJECT: GRB 160408A: Fermi GBM detection
DATE:    16/04/08 15:23:19 GMT
FROM:    Oliver Roberts at UCD/Fermi  <oliver.roberts at ucd.ie>

O.J. Roberts (UCD) reports on behalf of the Fermi GBM Team:

"At 06:25:43.86 UT on the 8th of April 2016, the Fermi
Gamma-Ray Burst Monitor triggered and located GRB 160408A
(trigger 481789547 / 160408268), which was also detected by
Swift (Evans et al. 2008, GCN 19620). The GBM on-ground
location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger
time using the Swift XRT position is about 7 degrees.

The GBM light curve consists of two bright, short emission
episodes, with a duration (T90) of about 0.9 s (50-300 keV).
The time-averaged spectrum from T0-0.064 s to T0+0.384 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.76 +/- 0.10 and
the cutoff energy, parameterized as Epeak, is 914 +/- 184 keV.

The event fluence (10-1000 keV) in this time interval is
(1.25 +/- 0.08)E-06 erg/cm^2. The 64 ms peak photon flux
measured starting from T0+0 s in the 10-1000 keV band,
is 12.4 +/- 1.4 ph/s/cm^2.

A Band function fits the spectrum equally well, with
Epeak = 765 +/- 198 keV, alpha = -0.70 +/- 0.12, and
beta = -2.27 +/- 0.41.

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