TITLE:   GCN CIRCULAR
NUMBER:  40362
SUBJECT: GRB 250506A: Fermi GBM Observation
DATE:    25/05/06 13:07:40 GMT
FROM:    Rushikesh Sonawane  at IISER, TVM <rushikesh23@iisertvm.ac.in>

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

"At 02:23:22.60 UT on 06 May 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250506A (trigger 768191007/250506100).
which was also detected by SVOM/ECLAIRs (Wang et al. 2025, GCN 40358).
The Fermi GBM on-ground location is consistent with the SVOM/ECLAIRs position.

The angle from the Fermi LAT boresight is 116 degrees.

The GBM light curve consists of multiple emission episodes with a duration (T90)
of about 48 s (50-300 keV). The time-averaged spectrum
from T0+0.003 to T0+61.441 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.07 +/- 0.04 and the cutoff energy,
parameterized as Epeak, is 280 +/- 20 keV.

The event fluence (10-1000 keV) in this time interval is
(2.36 +/- 0.06)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+34 s in the 10-1000 keV band is 27.4 +/- 0.5 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/"