TITLE:   GCN CIRCULAR
NUMBER:  43120
SUBJECT: GRB 251214B: Fermi GBM Observation
DATE:    25/12/15 13:26:50 GMT
FROM:    Marianna Dafčíková at Masaryk University <500025@mail.muni.cz>

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

"At 09:02:18.03 UT on 14 December 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 251214B (trigger 787395743/251214377),
which was also detected by Swift BAT (R. A. J. Eyles-Ferris et al. 2025, GCN 43089)
and GECAM-B (X. H. Luo et al. 2025, GCN 43113).
The Fermi GBM on-ground location is consistent with the Swift BAT position.

The angle from the Fermi LAT boresight is 97 degrees.

The GBM light curve consists of a double-peaked emission with a duration (T90)
of about 15 s (50-300 keV). The time-averaged spectrum
from T0-0.6 to T0+9.9 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.81 +/- 0.05 and the cutoff energy,
parameterized as Epeak, is 1280 +/- 80 keV.

The event fluence (10-1000 keV) in this time interval is
(1.3 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.58 s in the 10-1000 keV band is 3.3 +/- 0.3 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/"