{
  "circularId": 39502,
  "createdOn": 1740609484882,
  "submittedHow": "web",
  "bibcode": "2025GCN.39502....1G",
  "eventId": "GRB 250225B",
  "format": "text/plain",
  "body": "M. Godwin (UAH), C. Meegan (UAH), P. Veres (UAH) and R. Hamburg (USRA) report on behalf of\nthe Fermi Gamma-ray Burst Monitor Team:\n\n\"At 19:39:13.83 UT on 25 February 2025, the Fermi Gamma-ray Burst Monitor (GBM)\ntriggered and located GRB 250225B (trigger 762205158/250225819).\nwhich was also detected by Swift BAT (H. A. Krimm et al. 2025, GCN 39473), Konus-Wind (A. Tsvetkova et al. 2025, GCN 39498), and VLT/FORS2 (Schneider et al. 2025, GCN 39494)\nThe Fermi GBM on-ground location is consistent with the Swift BAT position.\n\nThe angle from the Fermi LAT boresight is 55 degrees.\n\nThe GBM light curve consists of one bright peak followed my multiple short peaks with a duration (T90)\nof about 335 s. The time-averaged spectrum\nfrom T0-3.6 to T0+340.5 s is best fit by\na power law function with an exponential high-energy cutoff.The power law index is -1.30 +/- 0.05  and the cutoff energy, parameterized as Epeak, is 218 +/- 28 keV.\n\nThe event fluence (10-1000 keV) in this time interval is\n(2.14 +/- 0.11)E-05 erg/cm^2. The 1-sec peak photon flux measured\nstarting from T0+1.3 s in the 10-1000 keV band is 21.9 +/- 0.3 ph/s/cm^2.\n\nThe time-averaged spectrum of the first peak from T0 to T0+3.6 s is best fit by\na power law function with an exponential high-energy cutoff. The power law index is -1.06 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 568 +/- 42 keV. The Band function fits the spectrum equally well, with an Epeak of 547 +/- 46 keV, alpha = -1.05 +/- 0.03 and beta = -2.85 +/-0.67. \n\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/\"",
  "submitter": "Matt Godwin <msg0028@uah.edu>",
  "subject": "GRB 250225B: Fermi GBM Observation"
}