GCN Circular 42881
Subject
GRB 251128A: Fermi GBM Observation
Event
Date
2025-11-29T03:48:05Z (a day ago)
From
rhamburg@usra.edu
Via
Web form
R. Hamburg (USRA), M. Godwin (UAH), Padraig McDermott (UCD), and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 04:22:21.61 UT on 28 November 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251128A (trigger 785996546/251128182; GCN 42865), which was also detected by Swift/BAT-GUANO (DeLaunay et al. 2025, GCN 42874).
The angle from the Fermi LAT boresight is 114 degrees.
The GBM light curve consists of multiple peaks with a duration (T90) of about 47 s (50-300 keV). The time-averaged spectrum from T0-0.0 to T0+44 s is best fit by a Band function with Epeak = 124 +/- 2, alpha = -0.92 +/- 0.01, and beta = -2.0 +/- 0.03.
The event fluence (10-1000 keV) in this time interval is (1.95 +/- 0.13)e-05 ergs/cm^2. The 1-sec peak photon flux measured starting from T0+9.1 s in the 10-1000 keV band is 11.8 +/- 0.5 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/"