TITLE:   GCN CIRCULAR
NUMBER:  39680
SUBJECT: GRB 250228A: Fermi GBM Observation
DATE:    25/03/12 07:13:25 GMT
FROM:    Utkarsh Pathak at IIT Bombay <utkarshpathak.07@gmail.com>

U. Pathak (IIT Bombay), M. Dafčíková (Masaryk U.), and C. Meegan (UAH) report 
on behalf of the Fermi Gamma-ray Burst Monitor Team:

"At 07:23:46.16 UT on 28 February 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250228A (trigger 762420231/250228308).
which was also detected by Swift/BAT-GUANO (Ronchini et al. 2025, GCN 39674).
The Fermi GBM on-ground location is consistent with the Swift/BAT position.

The angle from the Fermi LAT boresight is 27 degrees.

The GBM light curve consists of a weak pulse from a single emission episode
with a duration (T90) of about 0.6 s (50-300 keV). The time-averaged spectrum
from T0-0.5 to T0+0.3 s is best fit by
a simple power law function with index -1.45 +/- 0.1.

The event fluence (10-1000 keV) in this time interval is
(2.0 +/- 0.3)E-07 erg/cm^2. The 64-ms peak photon flux measured
starting from T0-0.064 s in the 10-1000 keV band is 4.3 +/- 0.9 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/"