TITLE: GCN CIRCULAR NUMBER: 35444 SUBJECT: GRB231230A: Fermi GBM Observation DATE: 23/12/30 18:40:14 GMT FROM: Cori Fletcher at USRA <cfletcher@usra.edu> C. Fletcher (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 01:29:10.05 UT on 30 December 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB231230A (trigger 725592555/231230062). which was also detected by Swift-BAT (Moss et al. 2023, GCN 35436). The Fermi GBM Real-time Localization (GCN 35434) is consistent with the Swift-BAT position. The angle from the Fermi LAT boresight is 157 degrees. The GBM light curve consists of multiple spikes with a duration (T90) of about 17 s (50-300 keV). The time-averaged spectrum from T0-2.6 to T0+17.9 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.2 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 220 +/- 40 keV. The event fluence (10-1000 keV) in this time interval is (6.1 +/- 0.5)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+9.3 s in the 10-1000 keV band is 5 +/- 1 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/" View this GCN Circular online at https://gcn.nasa.gov/circulars/35444. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...