TITLE: GCN CIRCULAR NUMBER: 42175 SUBJECT: GRB 251006A: Fermi GBM Observation DATE: 25/10/09 15:08:56 GMT FROM: Eva MP eva.palafox@gmail.com

E. Palafox (INAOE), M. Godwin (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:

"At 13:27:35.03 UT on 06 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251006A (trigger 781450060/251006561), which was also detected by Swift/BAT-GUANO (J. DeLaunay et al. 2025, GCN 42144) and Glowbug (C. C. Cheung et al. 2025, GCN 42130). The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position.

The angle from the Fermi LAT boresight is 30 degrees.

The GBM light curve consists of one short emission with total duration (T90) of about 1.4 s (50-300 keV). The time-averaged spectrum from T0-0.3 to T0+0.3 s is best fit by a Comptonized function with Epeak of 490 +/- 170 and alpha of -0.9 +/- 0.2.

The event fluence (10-1000 keV) in this time interval is (4.8 +/- 0.6)E-07 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.0 s in the 10-1000 keV band is 7 +/- 1 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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