{
  "submitter": "Christian Malacaria at INAF-OAR <cmalacaria.astro@gmail.com>",
  "submittedHow": "web",
  "createdOn": 1781619647435,
  "format": "text/markdown",
  "eventId": "GRB 260616B",
  "circularId": 44953,
  "subject": "GRB 260616B: Fermi GBM Detection",
  "body": "C. Malacaria (INAF-OAR) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:\n\n\"At 07:05:16.39 UT on 16 June 2026, the Fermi Gamma-ray Burst Monitor (GBM)\ntriggered and located GRB 260616B (trigger 803286321/260616295).\n\nThe on-ground calculated location, using the Fermi GBM trigger data,\nis RA = 257.49, Dec = -32.62 (J2000 degrees, equivalent to\nJ2000 17h 9m, -32d 37'), with a statistical uncertainty of 1.70 degrees.\n(radius, 1-sigma containment, statistical only; there is additionally a systematic error\nwhich we have characterized as a core-plus-tail model, with 90% of GRBs having a\n3.7 deg error and a small tail suffering a larger than 10 deg systematic error\n[Connaughton et al. 2015, ApJS, 216, 32]).\n\nThe angle from the Fermi LAT boresight is 76 degrees.\n\nThe GBM light curve consists of two main pulses with a duration (T90)\nof about 13.8 s (50-300 keV). The time-averaged spectrum\nfrom T0+0.002 to T0+14.464 s is best fit by\na Band function with Epeak = 240 +/- 10 keV,\nalpha = -0.63 +/- 0.04, and beta = -2.09 +/- 0.06.\n\nThe event fluence (10-1000 keV) in this time interval is\n(2.03 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured\nstarting from T0+10 s in the 10-1000 keV band is 21.3 +/- 0.4 ph/s/cm^2.\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/\""
}