{
  "format": "text/plain",
  "subject": "GRB 260105B: Fermi GBM Detection",
  "eventId": "GRB 260105B",
  "createdOn": 1767744526794,
  "submitter": "Matt Godwin <msg0028@uah.edu>",
  "circularId": 43346,
  "submittedHow": "web",
  "bibcode": "2026GCN.43346....1G",
  "body": "Matt Godwin (UAH) and C. Meegan (UAH) report on behalf of\nthe Fermi Gamma-ray Burst Monitor Team:\n\n\"At 23:21:36.55 UT on 05 January 2026, the Fermi Gamma-ray Burst Monitor (GBM)\ntriggered and located GRB 260105B (trigger 789348101/260105973).\n\nThe on-ground calculated location, using the Fermi GBM trigger data,\nis RA = 259.71, Dec = 1.74 (J2000 degrees, equivalent to\nJ2000 17h 18m, +1d 44'), with a statistical uncertainty of 2.03 degrees.\n(radius, 1-sigma containment, statistical only; there is additionally a\nsystematic error which we have characterized as a mixture of two Gaussians,\none with a radius of 1.8 degrees (52% contribution) and one with a radius\nof 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]).\n\nThe angle from the Fermi LAT boresight is 68 degrees.\n\nThe GBM light curve consists of a single emission episode with a duration (T90)\nof about 11 s (50-300 keV). The time-averaged spectrum\nfrom T0-1.9 to T0+12.5 s is best fit by\na power law function with an exponential high-energy cutoff.\nThe power law index is -0.96 +/- 0.01 and the cutoff energy,\nparameterized as Epeak, is 232 +/- 2 keV.\n\nThe event fluence (10-1000 keV) in this time interval is\n(8 +/- 0.4)E-06 erg/cm^2. The 1-sec peak photon flux measured\nstarting from T0+2.4 s in the 10-1000 keV band is 156 +/- 2 ph/s/cm^2.\n\nA Band function fits the spectrum equally well\nwith Epeak= 178 +/- 2 keV, alpha = -0.83 +/- 0.01 and beta = -2.19 +/- 0.03.\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/\""
}