{
  "eventId": "GRB 251028B",
  "body": "C. Malacaria (INAF-OAR) report \non behalf of the Fermi Gamma-ray Burst Monitor Team:\n\n\"At 07:48:06.71 UT on 28 October 2025, the Fermi Gamma-ray Burst Monitor (GBM)\ntriggered and located GRB 251028B (trigger 783330491/251028325),\nwhich was also detected by the Glowbug (Woolf et al. 2025, GCN 42507) \nand Swift/BAT-GUANO (DeLaunay et al. 2025, GCN 42508).\nA final Fermi/GBM localization correction was issued in GCN 42502.\n\nThe GBM light curve consists of two main pulses with a duration (T90)\nof about 14 s (50-300 keV). The time-averaged spectrum from T0-0.3 s to T0+12.0 s \nis best fit by a power law function with an exponential high-energy cutoff.\nThe power law index is -0.77 +/- 0.10 and the cutoff energy, parameterized as \nEpeak, is 125 +/- 8 keV.\n\nThe event fluence (10-1000 keV) in this time interval is\n(3.9 +/- 0.2)E-06 erg/cm^2. The 1.024-sec peak photon flux measured\nstarting from T0+8.9 s in the 10-1000 keV band\nis 6.4 +/- 0.4 ph/s/cm^2.\n\nA Band function fits the spectrum equally well with Epeak = 113 +/- 11 keV, \nalpha = -0.68 +/- 0.14 and beta = -2.8 +/- 0.4.\n\nThe spectral analysis results presented above are preliminary;\nfinal results will be published in the GBM GRB Catalog.\"",
  "format": "text/plain",
  "bibcode": "2025GCN.42509....1M",
  "submitter": "Christian Malacaria at INAF-OAR <cmalacaria.astro@gmail.com>",
  "circularId": 42509,
  "subject": "GRB 251028B: Fermi/GBM observation",
  "submittedHow": "web",
  "createdOn": 1761739174297
}