Skip to main content
Introducing Einstein Probe, Astro Flavored Markdown, and Notices Schema v4.0.0. See news and announcements

GCN Circular 35227

GRB 231129C: Fermi GBM Observation of a very bright GRB
2023-11-30T04:57:42Z (8 months ago)
Vidushi Sharma at NASA GSFC/UMBC <>
Web form
V. Sharma (NASA-GSFC/UMBC), C. Fletcher (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:

"At 19:10:18.11 UT on 29 November 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 231129C (trigger 722977823/231129799), which was also detected by MAXI/GSC (Y. Kawakubo et al. 2023, GCN 35223). The Fermi GBM Final Real-time Localization is reported (GCN 35221, GCN 35217).

The angle from the Fermi LAT boresight at the GBM trigger time is 50 degrees.

The GBM light curve shows a very bright, single pulse starting from about T0+0 s to T0+15 s. The calculated duration (T90) is about 6 s (50-300 keV). The time-averaged spectrum from T0+0 s to T0+7 s can be fit by a Band function with Epeak = 215 +/- 2 keV, alpha = -0.11 +/- 0.01, and beta = -2.79 +/- 0.03. 

The event fluence (10-1000 keV) in this time interval is (8.41 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1.8 s in the 10-1000 keV band is 102 +/- 1 ph/s/cm^2. 

The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog:

For Fermi GBM data and info, please visit the official Fermi GBM Support Page:"
Looking for U.S. government information and services? Visit