TITLE:   GCN CIRCULAR
NUMBER:  40717
SUBJECT: GRB 250612B: Fermi GBM Observation
DATE:    25/06/13 06:34:50 GMT
FROM:    Rushikesh Sonawane  at IISER, TVM <rushikesh23@iisertvm.ac.in>

R. Sonawane (IISER, TVM) and C. Meegan (UAH) report on behalf of
the Fermi Gamma-ray Burst Monitor Team:

"At 12:27:56.19 UT on 12 June 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250612B (trigger 771424081/250612519).
which was also detected by EP-WXT (Hua et al. 2025, GCN 40700).
The Fermi GBM on-ground location is consistent with the EP-WXT position.

The angle from the Fermi LAT boresight is 68 degrees.

The GBM light curve consists of single emission episode with a duration (T90)
of about 10.8 s (50-300 keV). The time-averaged spectrum
from T0-4.4 to T0+18.2 s is best fit by
a Band function with Epeak = 47.80 +/- 1.53 keV,
alpha = -0.92 +/- 0.09, and beta = -3.47 +/- 0.39.

A Comp model fits the spectrum equally well, with a power-law index = –0.98 +/- 0.07 
and cutoff energy parameterized as Epeak = 49.14 +/- 1.26 keV.

The event fluence (10-1000 keV) in this time interval is
(5.2 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2.9 s in the 10-1000 keV band is 12.1 +/- 0.3 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/"