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/"
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