{
  "eventId": "GRB 250509A",
  "format": "text/plain",
  "bibcode": "2025GCN.40422....1M",
  "subject": "GRB 250509A: Fermi GBM Observation",
  "createdOn": 1746895878189,
  "submittedHow": "web",
  "body": "A. Myers (NPP/GSFC), C. Meegan (UAH) and A. Holzmann Airasca (UniTrento and INFN Bari) report on behalf of\nthe Fermi Gamma-ray Burst Monitor Team:\n\n\"At 22:33:29.29 UT on 09 May 2025, the Fermi Gamma-ray Burst Monitor (GBM)\ntriggered and located GRB 250509A (trigger 768522814/250509940).\nwhich was also detected by Swift BAT (M. H. Siegel et al. 2025, GCN 40407).\nThe Fermi GBM on-ground location is consistent with the Swift BAT position.\n\nThe angle from the Fermi LAT boresight is 89 degrees.\n\nThe GBM light curve consists of main emission episode with a duration (T90)\nof about 69 s (50-300 keV). The time-averaged spectrum\nfrom T0+0.000 to T0+69.120 s is best fit by\na power law function.\nThe power law index is -2.19 +/- 0.03.\n\nThe event fluence (10-1000 keV) in this time interval is\n(6.18 +/- 0.29)E-06 erg/cm^2. The 1-sec peak photon flux measured\nstarting from T0+6.2 s in the 10-1000 keV band is 3.6 +/- 0.3 ph/s/cm^2.\n\nThe spectral analysis results presented above are preliminary;\nfinal results will be published in the GBM GRB Catalog:\nhttps://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html\n\nFor Fermi GBM data and info, please visit the official Fermi GBM Support Page:",
  "circularId": 40422,
  "submitter": "Ava Myers at NASA GSFC <ava.myers@nasa.gov>"
}