TITLE:   GCN CIRCULAR
NUMBER:  30519
SUBJECT: GRB 210725A: Fermi GBM detection
DATE:    21/07/26 16:48:00 GMT
FROM:    Suraj Poolakkil at UAH  <sp0076@uah.edu>

S. Poolakkil (UAH) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 03:47:03.54 UT on 25 July 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210725A (trigger 648877628 / 210725158)
which was also detected by the Swift/BAT (Bernardini et al. 2021, GCN
30501).
The GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight at the GBM trigger time is 78
degrees.

The GBM light curve consists of a single peak followed by some
extended emission with a duration (T90) of about 47 s (50-300 keV).
The time-averaged spectrum from T0-1.02 s to T0+9.21 s
is best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.37 +/- 0.22  and
the cutoff energy, parameterized as Epeak, is 460 +/- 104 keV.

The event fluence (10-1000 keV) in this time interval is
(3.14 +/- 0.35)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.64 s in the 10-1000 keV band
is 2.0 +/- 0.2 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html

For Fermi GBM data and info, please visit the official Fermi GBM Support
Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"