TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2909 SUBJECT: GRB 041223 Fluence measured by Swift-BAT DATE: 04/12/25 01:41:53 GMT FROM: Craig Markwardt at NASA/GSFC/UMD GRB041223 Fluence measured by Swift-BAT C. Markwardt (GSFC/UMD), M. Suzuki (Saitama), L. Barbier, S. Barthelmy (GSFC), J. Cummings (GSFC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA), K. McLean, D. Palmer (LANL), A. Parsons (GSFC), G. Sato (ISAS), J. Tueller (GSFC), on behalf of the Swift BAT team: GRB 041223 (Tueller et al., GCN #2898) was a spectrally hard burst. Fits to the total Swift-BAT burst spectrum are consistent with a power law, with a photon index of 1.05-1.15. The BAT team did not quote a total band fluence in GCN 2898, due to uncertainty in the response at high energies. Now, with further simulations and spectral analysis, we estimate that the 15-350 keV fluence was ~5E-5 erg/cm^2. The peak flux was 3E-6 erg/cm^2/s (15-350 keV; 1 s sampling), which is dominated by the highest energy band.