TITLE:   GCN CIRCULAR
NUMBER:  40833
SUBJECT: GRB250625A: Fermi GBM Observation
DATE:    25/06/26 03:47:05 GMT
FROM:    Matt Godwin <msg0028@uah.edu>

Matt Godwin (UAH), O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 16:04:57.51 UT on 25 June 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB250625A (trigger 772560302/250625670).
Which was also detected by Swift BAT/XRT (Ferro et al. 2025, GCN 40825) and SVOM/VT (Xin et al. 2025, GCN 40830).
The Fermi GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight is 32 degrees.

The GBM light curve consists of one strong peak and a few weaker peaks with a duration (T90)
of about 5.4 s (50-300 keV). The time-averaged spectrum
from T0-2.0 to T0+5.0 s is best fit by
a power law function with an exponential high-energy cutoff. The power law index is -1.27 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 1301.00 +/- 1190.00

The event fluence (10-1000 keV) in this time interval is
(1.8 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.13 s in the 10-1000 keV band is 3 +/- 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/"