TITLE: GCN CIRCULAR NUMBER: 38668 SUBJECT: GRB 241223A: Fermi GBM Detection DATE: 24/12/25 06:06:58 GMT FROM: Rushikesh Sonawane at IISER, TVM <rushikesh23@iisertvm.ac.in> R. Sonawane (IISER, TVM) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 12:08:46.63 UT on 23 December 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 241223A (trigger 756648531/241223506). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 159.85, Dec = -34.80 (J2000 degrees, equivalent to J2000 10h 39m, -34d 47'), with a statistical uncertainty of 1.00 degrees. (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a mixture of two Gaussians, one with a radius of 1.8 degrees (52% contribution) and one with a radius of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]). The angle from the Fermi LAT boresight is 67 degrees. The GBM light curve consist of one weak emission episode (possibly a precursor) followed by a strong emission episode with a duration (T90) of about 30.5 s (50-300 keV). The time-averaged spectrum from T0+0.003 to T0+47.489 s is best fit by a Band function with Epeak = 239 +/- 5 keV, alpha = -0.66 +/- 0.02, and beta = -2.42 +/- 0.06. The event fluence (10-1000 keV) in this time interval is (6.28 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+26 s in the 10-1000 keV band is 34.4 +/- 0.4 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/38668. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...