{
  "bibcode": "2018GCN.22822....1S",
  "body": "D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks,\nM. Ulanov, A. Tsvetkova, A. Lysenko, A. Kozlova, and T. Cline\non behalf of the Konus-Wind team, report:\n\nThe bright, short-duration, hard GRB 180618A\n(Swift-BAT detection: LaPorte et al., GCN Circ 22790;\nFermi-GBM detection: Hamburg et al., GCN Circ 22794)\ntriggered Konus-Wind at T0=2591.201 s UT (00:43:11.201).\n\nThe burst light curve shows a bright multi-peaked initial pulse\nwith a total duration of ~0.250 s, followed by\nan extended emission seen up to ~T0+10 s.\nThe emission of the initial pulse is seen up to ~10 MeV.\n\nThe Konus-Wind light curve of this GRB is available at\nhttp://www.ioffe.ru/LEA/GRBs/GRB180618_T02591/\n\nAs observed by Konus-Wind, the burst\nhad a fluence of 6.24(-1.13,+1.20)x10^-6 erg/cm2,\nand a 16-ms peak flux, measured from T0-0.010 s,\nof 5.60(-1.83,+1.88)x10^-5 erg/cm2/s\n(both in the 20 keV - 10 MeV energy range).\n\nThe time-averaged spectrum of the initial pulse\n(measured from T0 to T0+0.192 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 = -0.36(-0.24,+0.30)\nand Ep = 2461(-565,+788) keV (chi2 = 47/38 dof).\nFitting by a GRB (Band) model yields the same alpha and Ep,\nand an upper limit on the high energy photon index: beta < -2.4\n(chi2 = 47/37 dof).\n\nThe time-averaged spectrum of the extended emission\n(measured from T0+0.256 to T0+8.448 s)\nis best fit in the 20 keV - 2 MeV range\nby the CPL model with alpha = -0.68(-0.79,+1.59),\nEp = 170(-66,+203) keV (chi2 = 102/98 dof).\n\nAmong ~300 bursts from the Konus catalog of short GRBs\n(Svinkin et al., 2016, ApJS 224, 10), GRB 180618A is within top 1%\nin the terms of 16-ms peak energy flux and within top 15% in the terms\nof the total energy fluence, both in the 20 keV - 10 MeV range.\nIn the terms of Epeak, the burst is within 1% hardest\nGRBs in the sample.\n\nAll the quoted errors are at the 90% confidence level.\nAll the quoted values are preliminary.",
  "circularId": 22822,
  "createdOn": 1529663571000,
  "email": "svinkin@mail.ioffe.ru",
  "subject": "Konus-Wind observation of GRB 180618A (a short GRB with extended emission)",
  "submitter": "Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>",
  "eventId": "GRB 180618A"
}