GCN Circular 40612

Jacob Smith (UAH) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

At 03:04:31.31 UT on 02 June 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250602A (trigger 770526276/250602128).
which was also detected by Fermi-LAT (A. Holzmann Airasca, et al. 2025, GCN 40611
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 ).
The Fermi GBM on-ground location is consistent with the Fermi-LAT position.

The angle from the Fermi LAT boresight is 111 degrees.

The GBM light curve consists of a single emission episode with a duration (T90)
of about 14.6 s (50-300 keV). The time-averaged spectrum
from T0+0.003 to T0+8.768 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.9 +/- 0.1 and the cutoff energy,
parameterized as Epeak, is 120 +/- 10 keV.

The event fluence (10-1000 keV) in this time interval is
(1.7 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.0 s in the 10-1000 keV band is 5.8 +/- 0.3 ph/s/cm^2.

A Band function fits the spectrum equally well
with Epeak= 102 +/- 22 keV, alpha = -0.7 +/- 0.3 and beta = -2.2 +/- 0.2.

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/