TITLE: GCN CIRCULAR NUMBER: 36024 SUBJECT: GRB 240403A: Fermi GBM Detection DATE: 24/04/04 14:27:05 GMT FROM: rachel.hamburg@ijclab.in2p3.fr R. Hamburg (CNRS/IN2P3/IJCLab), S. Dalessi (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 11:57:30.58 UT on 03 April 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240403A (trigger 733838255/240403498). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 6.5, Dec = -17.3 (J2000 degrees, equivalent to J2000 +00h 26m, -17d 17'), with a statistical uncertainty of 1.77 degrees. There is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error (Connaughton et al. 2015, ApJS, 216, 32). The angle from the Fermi LAT boresight is 62 degrees. The GBM light curve shows a precursor, a main emission peak and third weaker peak, yielding a duration (T90) of about 35.6 s (50-300 keV). The time-averaged spectrum from T0-1.2 to T0+76.7 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.11 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 350 +/- 10 keV. A Band function also fits well with Epeak = 322 +/- 14 keV, alpha = -1.08 +/- 0.02, and beta = -2.40 +/- 0.13. The event fluence (10-1000 keV) in this time interval is (3.6 +/- 0.4)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+26 s in the 10-1000 keV band is 39.1 +/- 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/36024. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...