GCN Circular 42957
Subject
GRB 251202A: Fermi GBM Observation
Event
Date
2025-12-02T16:57:29Z (a day ago)
From
Suman Bala at USRA <sumanbala2210@gmail.com>
Via
Web form
S. Bala (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 01:50:52.31 UT on 02 December 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 251202A (GCN trigger 786333057/251202077),
which was also detected by Einstein Probe (Y. J. Zhang et al. 2025, GCN 42937),
Swift XRT (B. Sbarufatti et al. 2025, GCN 42943), Swift UVOT (N.P.M. Kuin et al. 2025, GCN 42956)
GOTO (D. O’Neill et al. 2025, GCN 42947) and LCO (J. Quirola-Vasquez et al. 2025, GCN 42948).
The spectroscopic redshift of GRB 251202A is found to be 2.785 by NOT (Z.P. Zhu et al. 2025, GCN 42939).
The Fermi GBM Final Real-time Localization (GCN 42933) is consistent with the position reported by other instruments.
The angle from the Fermi LAT boresight is 73 degrees.
The GBM light curve consists of a single emission episode with a duration (T90)
of about 43 s (50-300 keV). The time-averaged spectrum
from T0-10 to T0+55 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.07 +/- 0.06 and the cutoff energy,
parameterized as Epeak, is 350 +/- 50 keV.
The event fluence (10-1000 keV) in this time interval is
(9.9 +/- 0.6)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+8.8 s in the 10-1000 keV band is 4.2 +/- 0.2 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/"