TITLE:   GCN CIRCULAR
NUMBER:  40114
SUBJECT: GRB 250407A: Fermi GBM Detection
DATE:    25/04/08 01:28:16 GMT
FROM:    oindabimukherjee@gmail.com

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

"At 15:48:21.07 UT on 07 April 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250407A (trigger 765733706/250407659). 
The afterglow was detected by ART-XC (Molkov et al. 2025, GCN 40110) 
and Swift-XRT (Dichiara et al. 2025, GCN 40113).

The Fermi GBM Final Localization (GCN 40104) is consistent with the ART-XC
and Swift-XRT positions.

The angle from the Fermi LAT boresight is 116 degrees.

The GBM light curve consists of a single-peak emission episode with a duration (T90)
of about 6.3 s (50-300 keV). The time-averaged spectrum
from T0+0.6 to T0+5.1 s is best fit by
a Band function with Epeak = 470 +/- 20 keV,
alpha = -0.18 +/- 0.03, and beta = -2.08 +/- 0.03.

The event fluence (10-1000 keV) in this time interval is
(2.65 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+0.77 s in the 10-1000 keV band is 62.4 +/- 0.7 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/"