{
  "circularId": 44931,
  "submitter": "Matt Godwin <msg0028@uah.edu>",
  "subject": "GRB 260610B: Fermi GBM Observation",
  "body": "Matt Godwin (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:\n\n\"At 23:46:14.25 UT on 10 June 2026, the Fermi Gamma-ray Burst Monitor (GBM)\ntriggered and located GRB 260610B (trigger 802827979/260610990).\nAn optical counterpart is identified by GOTO (O'Neill, et al. 2026, GCN 44903). The redshift of the source is measured to be z = 0.473, ALFOSC/NOT (ONeill et al. 2026, GCN 44914).\nThe Fermi GBM on-ground location is consistent with the GOTO position.\n\nThe angle from the Fermi LAT boresight is 97 degrees.\n\nThe GBM light curve consists of three peaks with a duration (T90)\nof about 62 s (50-300 keV). The time-averaged spectrum\nfrom T0-2.4 to T0+55.4 s is best fit by\na power law function with an exponential high-energy cutoff.\nThe power law index is -1.50 +/- 0.01 and the cutoff energy,\nparameterized as Epeak, is 46.8 +/- 0.4 keV.\n\nThe event fluence (10-1000 keV) in this time interval is\n(1.30 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured\nstarting from T0+3.8 s in the 10-1000 keV band is 7.7 +/- 0.3 ph/s/cm^2.\n\nA Band function fits the spectrum equally well\nwith Epeak= 45.9 +/- 0.5 keV, alpha = -1.4800 +/- 0.0009 and beta = -3.17 +/- 0.01.\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/\"",
  "eventId": "GRB 260610B",
  "submittedHow": "web",
  "createdOn": 1781374904066,
  "format": "text/plain"
}