TITLE:   GCN CIRCULAR
NUMBER:  40427
SUBJECT: GRB 250510B: Fermi GBM Observation
DATE:    25/05/11 05:33:44 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 06:41:54.06 UT on 10 May 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250510B (trigger 768552119/250510279).
which was also detected by Swift/BAT-GUANO (S. Ronchini et al. 2025, GCN 40419).
The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position.

The angle from the Fermi LAT boresight is 103 degrees.

The GBM light curve consists of main emission episode with a duration (T90)
of about 35 s (50-300 keV). The time-averaged spectrum
from T0+0.51 to T0+35.58 s is 
best fit by a Band function with Epeak = 147 +/- 15 keV,
alpha = 0.71 +/- 0.38, and beta = -2.79 +/- 0.49.

The event fluence (10-1000 keV) in this time interval is
(4.79 +/- 0.32)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2.01 s in the 10-1000 keV band is 2.44 +/- 0.22 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/"