[vsnet-grb-info 20955] GRB 170728A: Fermi GBM observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23053
SUBJECT: GRB 170728A: Fermi GBM observation
DATE:    18/07/29 04:18:59 GMT
FROM:    Peter Veres at UAH  <veresp at gmail.com>

P. Veres, C. Meegan, and B. Mailyan (all UAH)
report on behalf of the Fermi GBM Team:

"At 17:29:02.28 UT on 28 July 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180728A (trigger 554491747 / 180728728)
which was also detected by the Swift/BAT (Starling et al., GCN 23046).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 35 degrees.

The GBM light curve consists of a precursor and a very bright peak
with a duration (T90) of about 6.4 s (50-300 keV).
The time-averaged spectrum from T0+9.2s to T0+23.6 s is
best fit by a Band function with Epeak = 79.2 +/- 1.4 keV,
alpha = -1.54 +/- 0.01, and beta = -2.46 +/- 0.02.

The event fluence (10-1000 keV) in this time interval is
(5.65 +/- 0.02)E-5 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+11.1 s in the 10-1000 keV band
is 231.0 +/- 1.2 ph/s/cm^2.

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