TITLE:   GCN CIRCULAR
NUMBER:  42365
SUBJECT: GRB 251016A: Fermi GBM Observation
DATE:    25/10/18 23:23:26 GMT
FROM:    Jacob Smith at Fermi-GBM Team <jrs0118@uah.edu>

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

"At 14:59:19.76 UT on 16 October 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 251016A (trigger 782319564/251016625),
which is was detected by SVOM/ECLAIRs (Basa et al., GCN 42308), CALET-GBM (Kawakubo et al., GCN 42321), Glowbug (Woolf et al., GCN 42313) and Astro Sat CZTI (Arya et al., GCN 42327).
The Fermi GBM on-ground location is consistent with the SVOM/ECLAIRs position.

The angle from the Fermi LAT boresight is 42 degrees.

The GBM light curve consists of a single emission episode with a duration (T90)
of about 0.32 s (50-300 keV). The time-averaged spectrum
from T0-0.1 to T0+0.4 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -0.83 +/- 0.04 and the cutoff energy,
parameterized as Epeak, is 1317 +/- 145 keV.

The event fluence (10-1000 keV) in this time interval is
(3 +/- 0.08)E-06 erg/cm^2. The 64-ms peak photon flux measured
starting from T0+0.13 s in the 10-1000 keV band is 34 +/- 2 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/"