{
  "bibcode": "2025GCN.42340....1H",
  "submitter": "rhamburg@usra.edu",
  "subject": "GRB 251011A: Fermi GBM Observation",
  "submittedHow": "web",
  "body": "R. Hamburg (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:\n\n\"At 03:41:40.09 UT on 11 October 2025, the Fermi Gamma-ray Burst Monitor (GBM)\ntriggered and located GRB 251011A (trigger 781846905/251011154), which was also\ndetected by AstroSat (Tembhurnikar et al. 2025, GCN 42199), Insight-HMXT (Wang \net al. 2025, GCN 42210), and Swift-BAT/GUANO (DeLaunay et al. 2025, GCN 42245).\nThe Fermi GBM on-ground location is consistent with the Swift position.\n\nThe angle from the Fermi LAT boresight is 62 degrees.\n\nThe GBM light curve consists of a multi-peaked structure with a duration (T90)\nof about 4.9 s (50-300 keV). The time-averaged spectrum from T0-0.7 to T0+4.9 s\nis best fit by a power law function with an exponential high-energy cutoff.\nThe power law index is -0.76 +/- 0.01 and the cutoff energy, parameterized as \nEpeak, is 136 +/- 1 keV.\n\nThe event fluence (10-1000 keV) in this time interval is \n(3.26 +/- 0.07)E-06 ergs/cm^2 erg/cm^2. The 1-sec peak photon flux measured\nstarting from T0+1.8 s in the 10-1000 keV band is 11.5 +/- 0.3 ph/s/cm^2.\n\nA Band function fits the spectrum equally well with Epeak = 125 +/- 1 keV, \nalpha = -0.69 +/- 0.01 and beta = -2.70 +/- 0.04.\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:\nhttps://fermi.gsfc.nasa.gov/ssc/data/access/gbm/\"",
  "createdOn": 1760754435412,
  "eventId": "GRB 251011A",
  "format": "text/plain",
  "circularId": 42340
}