TITLE: GCN CIRCULAR NUMBER: 39751 SUBJECT: GRB 250316A: Fermi GBM Observation DATE: 25/03/17 03:14:06 GMT FROM: sumanbala2210@gmail.com

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

"At 08:59:57.69 UT on 16 March 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250316A (trigger 763808402/250316375). which was also detected by Swift/BAT-GUANO (Ronchini et al. 2025, GCN 39744). The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position.

The angle from the Fermi LAT boresight is 98 degrees.

The GBM light curve consists of multiple peaks with a duration (T90) of about 38.7 s (50-300 keV). The time-averaged spectrum from T0-3.1 to T0+46.1 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.2 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 110 +/- 10 keV.

The event fluence (10-1000 keV) in this time interval is (4.7 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+16 s in the 10-1000 keV band is 3.5 +/- 0.3 ph/s/cm^2.

A Band function fits the spectrum equally well with Epeak= 80 +/- 10 keV, alpha = -1 +/- 0.2 and beta = -2.3 +/- 0.2.

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/"

View this GCN Circular online at https://gcn.nasa.gov/circulars/39751. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...