TITLE: GCN CIRCULAR NUMBER: 40427 SUBJECT: GRB 250510B: Fermi GBM Observation DATE: 25/05/11 05:33:44 GMT FROM: A. Holzmann Airasca at University of Trento and INFN Bari a.holzmannairasca@unitn.it
A. Holzmann Airasca (UniTrento and INFN Bari) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 06:41:54.06 UT on 10 May 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250510B (trigger 768552119/250510279). which was also detected by Swift/BAT-GUANO (S. Ronchini et al. 2025, GCN 40419). The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position.
The angle from the Fermi LAT boresight is 103 degrees.
The GBM light curve consists of main emission episode with a duration (T90) of about 35 s (50-300 keV). The time-averaged spectrum from T0+0.51 to T0+35.58 s is best fit by a Band function with Epeak = 147 +/- 15 keV, alpha = 0.71 +/- 0.38, and beta = -2.79 +/- 0.49.
The event fluence (10-1000 keV) in this time interval is (4.79 +/- 0.32)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+2.01 s in the 10-1000 keV band is 2.44 +/- 0.22 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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