TITLE: GCN CIRCULAR NUMBER: 36416 SUBJECT: GRB 240504A: Fermi GBM Observation DATE: 24/05/08 18:41:31 GMT FROM: Bagrat Mailyan at Florida Tech B. Mailyan (Florida tech) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 05:12:52.64 UT on 04 May 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240504A (trigger 736492377/240504217). which was also detected by Swift/BAT-GUANO (S. Ronchini et al. 2024, GCN 36401). The Fermi GBM on-ground location is consistent with the Fermi GBM final position notice (GCN 36387). The angle from the Fermi LAT boresight is 64 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 19 s (50-300 keV). The time-averaged spectrum from T0+0.003 to T0+20.096 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.12 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 682.50 +/- 52.10. A Band function with Epeak 665.80 +/- 55.40, Alpha -1.11 +/- 0.02, Beta -3.01 +/- 0.77 fits the spectrum equally well. The event fluence (10-1000 keV) in this time interval is (2.26 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+6.7 s in the 10-1000 keV band is 11.5 +/- 0.3 ph/s/cm^2. We note that there is a second FRED-like peak about 100s after the reported event here that seems to be related. However, due to a contemporaneous solar flare, we are unable to disentangle the two events and thus we omit this portion of the burst due to contamination. We note that the burst could have a T90 of 250s, but other instruments are required to confirm this. 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/"