TITLE: GCN CIRCULAR NUMBER: 38529 SUBJECT: GRB 241129A: Fermi GBM Observation DATE: 24/12/10 18:23:02 GMT FROM: rhamburg@usra.edu

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

"At 01:31:33.42 UT on 29 November 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 241129A (trigger 754536698/241129064), which was also detected by Swift/BAT-NITRATES (DeLaunay et al. 2024, GCN 38419). The Fermi GBM on-ground location is consistent with the Swift position.

The angle from the Fermi LAT boresight is 75 degrees.

The GBM light curve consists of a multi-peaked emission episode with a duration (T90) of about 52 s (50-300 keV). The time-averaged spectrum from T0-2.0 to T0+22.5 s is best fit by a simple power law function with index -2.00 +/- 0.04.

The event fluence (10-1000 keV) in this time interval is (2.6 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.26 s in the 10-1000 keV band is 2.1 +/- 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/"

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