TITLE:   GCN CIRCULAR
NUMBER:  39964
SUBJECT: GRB 250330A: Fermi GBM Observation
DATE:    25/03/31 06:48:11 GMT
FROM:    Utkarsh Pathak at IIT Bombay <utkarshpathak.07@gmail.com>

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

"At 06:07:38.42 UT on 30 March 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250330A (trigger 765007663/250330255).
which was also detected by Swift-BAT (Cenko et al. 2025, GCN 39938).
The afterglow has been detected by Swift-XRT (Osborne et al. 2025, GCN 39947).
The Fermi GBM Final Localization (GCN 39944) is consistent with the Swift-BAT
and Swift-XRT positions (Page et al. 2025, GCN 39940).

The angle from the Fermi LAT boresight is 46 degrees.

The GBM light curve consists of a single emission episode with a duration
(T90) of about 4.8 s (50-300 keV). The time-averaged spectrum 
from T0-0.6 to T0+6.53 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 95 +/- 8 keV.

The event fluence (10-1000 keV) in this time interval is
(1.50 +/- 0.08)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.26 s in the 10-1000 keV band is 6.5 +/- 0.3 ph/s/cm^2.

A Band function fits the spectrum equally well
with Epeak= 86 +/- 10 keV, alpha = -0.8 +/- 0.2 and beta = -2.7 +/- 0.4.

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/"