TITLE:   GCN CIRCULAR
NUMBER:  41141
SUBJECT: GRB 250721A: Fermi GBM Observation
DATE:    25/07/23 14:43:37 GMT
FROM:    A. Holzmann Airasca at University of Trento and INFN Bari <a.holzmannairasca@unitn.it>

A. Holzmann Airasca (UniTrento and INFN Bari) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 09:37:46.53 UT on 21 July 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250721A (trigger 774783471/250721401).
which was also detected by MAXI (M. Nakajima et al. 2025, GCN 41129).
The Fermi GBM on-ground location is consistent with the MAXI position.

The angle from the Fermi LAT boresight is 70 degrees.

The GBM light curve consists of a single emission episode with a duration (T90)
of about 54 s (50-300 keV). The time-averaged spectrum
from T0-3.1 to T0+1.5 s is best fit by
a simple power law function with index -1.46 +/- 0.07.

The event fluence (10-1000 keV) in this time interval is
(9.8 +/- 1.6)E-07 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-2.5 s in the 10-1000 keV band is 1.7 +/- 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/"