TITLE: GCN CIRCULAR NUMBER: 36949 SUBJECT: GRB 240727B: Fermi GBM Observation DATE: 24/07/27 19:00:39 GMT FROM: Cori Fletcher at USRA <cfletcher@usra.edu> C. Fletcher (USRA), R. Hamburg (CNRS/IJCLab) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 06:00:08.96 UT on 27 July 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240727B (trigger 743752813/240727250). which was also detected by Swift/BAT-GUANO (Ronchini et al. 2024, GCN 36945) and AstroSat (Waratkar et al. 2024, GCN 36943). The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position. The angle from the Fermi LAT boresight is 114 degrees. The GBM light curve consists of multiple peaks with a duration (T90) of about 19 s (50-300 keV). The time-averaged spectrum from T0-3.3 to T0+20.2 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.3 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 850 +/- 90 keV. The event fluence (10-1000 keV) in this time interval is (1.52 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+8.7 s in the 10-1000 keV band is 3.4 +/- 0.4 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 848 +/- 116 keV, alpha = -0.3 +/- 0.1 and beta = -2.5 +/- 0.3. 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/36949. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...