TITLE: GCN CIRCULAR NUMBER: 42169 SUBJECT: GRB 251006B: Fermi GBM Observation DATE: 25/10/08 18:01:32 GMT FROM: Matt Godwin msg0028@uah.edu
Matt Godwin (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 20:05:04.04 UT on 06 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251006B (trigger 781473909/251006837), which was also detected by Einstein Probe (Yin et al. 2025, GCN 42137) and SVOM/GRM (Wang et al. 2025, GCN 42139). The Fermi GBM on-ground location is consistent with the EP position.
The angle from the Fermi LAT boresight is 104 degrees.
The GBM light curve consists of one bright emission with a weaker secondary peak with total duration (T90) of about 5.9 s (50-300 keV). The time-averaged spectrum from T0-2.0 to T0+7.2 s is best fit by a Band function with Epeak = 330 +/- 14 keV, alpha = -0.61 +/- 0.03, and beta = -2.4 +/- 0.1.
The event fluence (10-1000 keV) in this time interval is (2.06 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.38 s in the 10-1000 keV band is 26.2 +/- 0.4 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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