{
  "format": "text/plain",
  "circularId": 43222,
  "subject": "GRB 251222A: Fermi GBM Observation",
  "body": "Eliza Neights (GWU, NASA GSFC) and C. Meegan (UAH) report on behalf of\nthe Fermi Gamma-ray Burst Monitor Team:\n\n\"At 17:05:51.27 UT on 22 December 2025, the Fermi Gamma-ray Burst Monitor (GBM)\ntriggered and located GRB 251222A (trigger 788115956/251222712).\nwhich was also detected by SVOM ECLAIRs, GRM, and MXT (H. Yang et al. 2025, GCN 43188), \nSVOM VT (J. T. Palmerio et al. 2025, GCN 43189), NOT (J. An et al. 2025, GCN 43194), \nCalapai Observatory (G. Calapai et al. 2025, GCN 43195), PRIME (J. Durbak et al. 2025, GCN 43197),\nEP WXT (C.-L. Guo et al. 2025, GCN 43201), DFOT (A. Gupta et al. 2025, GCN 43207), \nLCO (A. Saccardi et al. 2025, GCN 43208; I. Pérez-Fournon et al. 2025, GCN 43212), \nGOTO (A. Kumar et al. 2025, GCN 43209), Swift XRT (A.P. Beardmore et al. 2025, GCN 43213), \nand Konus Wind (D. Frederiks et al. 2025, GCN 43214).\nThe spectroscopic redshift of GRB 251222A is found to be 3.171 by VLT/X-shooter (A. Saccardi et al. 2025, GCN 43204).\nThe Fermi GBM on-ground location is consistent with the position reported by other instruments.\n\nThe angle from the Fermi LAT boresight is 83 degrees.\n\nThe GBM light curve consists of multiple emission episodes with a duration (T90)\nof about 83 s (50-300 keV). The time-averaged spectrum\nfrom T0-2.2 to T0+91.7 s is best fit by\na power law function with an exponential high-energy cutoff.\nThe power law index is -1.26 +/- 0.01 and the cutoff energy,\nparameterized as Epeak, is 118 +/- 1 keV.\n\nThe event fluence (10-1000 keV) in this time interval is\n(1.09 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured\nstarting from T0+54 s in the 10-1000 keV band is 9.5 +/- 0.3 ph/s/cm^2.\n\nA Band function fits the spectrum equally well\nwith Epeak= 64.9 +/- 0.8 keV, alpha = -0.84 +/- 0.01 and beta = -2.0 +/- 0.02.\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/\"",
  "bibcode": "2025GCN.43222....1N",
  "eventId": "GRB 251222A",
  "submittedHow": "web",
  "submitter": "eliza.neights@gmail.com",
  "createdOn": 1766515199432
}