[vsnet-grb-info 15419] GRB 140818A - Fermi GBM Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  16708
SUBJECT: GRB 140818A - Fermi GBM Detection
DATE:    14/08/18 18:08:23 GMT
FROM:    Oliver Roberts at UCD/Fermi  <oliver.roberts at ucd.ie>

Oliver Roberts (UCD) reports on behalf of the Fermi GBM Team:

"At 05:30:09.12 UT on the 18th of August 2014, the Fermi Gamma-Ray
Burst Monitor triggered and located GRB 140818A (trigger 430032612
/ 140818229), which was also detected by MAXI/GSC (H. Negoro et al.
GCN 16702 and GCN 16705). A possible afterglow has also been reported
by Swift-XRT and UVOT (C. Swenson et al. GCN 16706)  The GBM
on-ground location is consistent with the MAXI/GSC and Swift positions.
The angle from the Fermi LAT boresight is 35 degrees.

The GBM light curve consists of two peaks, with the second peak
at T~50s being brighter than the first. The duration (T90) of the
burst is about 109 s (50-300 keV). The time-averaged spectrum from
T0+25s to T0+135 s is adequately fit by a BAND function. The power
law index alpha is -0.69 +/- 0.04 . The power law index beta is
-2.39 +/- 0.10 . The cutoff energy, parameterised as Epeak, is
181 +/- 8 keV.

The event fluence (10-1000 keV) in this time interval is
(2.95 +/- 0.06)E-05 erg/cm^2. The 1.024-sec peak photon flux was
measured starting from T0+99.5 s in the 10-1000 keV band is
8.6 +/- 0.3 ph/s/cm^2.

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