{
  "eventId": "GRB 260518A",
  "bibcode": "2026GCN.44671....1S",
  "submittedHow": "web",
  "submitter": "Dmitry Svinkin at Ioffe Institute <dmitrysvinkin@gmail.com>",
  "createdOn": 1779229080724,
  "subject": "Konus-Wind detection of GRB 260518A",
  "circularId": 44671,
  "format": "text/plain",
  "body": "D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia,\nA. Tsvetkova, M. Ulanov, and T. Cline\non behalf of the Konus-Wind team, report:\n\nThe long-duration GRB 260518A\n(AstroSat-CZTI detection: Harsha et al., GCN 44668)\ntriggered Konus-Wind at T0=27873.529 s UT (07:44:33.529).\n\nThe burst light curve shows a multipeaked structure\nwhich starts at ~T0-9 s and has a total duration of ~18 s.\nThe emission is seen up to ~1 MeV.\n\nThe Konus-Wind light curve of this GRB is available at\nhttp://www.ioffe.ru/LEA/GRBs/GRB260518_T27873/\n\nAs observed by Konus-Wind, the burst\nhad the total fluence of 4.59(-0.38,+0.42)x10^-6 erg/cm2,\nand the 64-ms peak flux, measured from T0-0.016 s,\nof 2.35(-0.47,+0.48)x10^-6 erg/cm2/s\n(both in the 20 keV - 10 MeV energy range).\n\nThe time-averaged spectrum of the burst\n(measured from T0 to T0+8.448 s)\nis best fit in the 20 keV - 10 MeV range\nby a power law with exponential cutoff model:\ndN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)\nwith alpha = -0.11(-0.36,+0.42)\nand Ep = 213(-24,+31) keV (chi2 = 66/85 dof).\nFitting by a GRB (Band) model yields the same alpha and Ep,\nand an upper limit on the high energy photon index: beta < -2.9\n(chi2 = 66/84 dof).\n\nAll the quoted errors are at the 68% confidence level.\nAll the quoted values are preliminary."
}