{
  "bibcode": "2023GCN.33427....1S",
  "body": "D. Svinkin, D. Frederiks, M. Ulanov, A. Tsvetkova,\nA. Lysenko, A. Ridnaia, and T. Cline\non behalf of the Konus-Wind team, report:\n\nThe very intense, long-duration GRB 230307A\n(Fermi-GBM detection: the Fermi GBM team, GCN Circ. 33405;\nDalessi, GCN Circ. 33407; Dalessi and Roberts, GCN Circ. 33411;\nGECAM detection: Xiong et al., GCN Circ. 33406;\nSolar Orbiter STIX detection: Xiao and Krucker, GCN Circ. 33410;\nAGILE-MCAL detection: Casentini et al., GCN Circ. 33412;\nIPN triangulation: Kozyrev et al., GCN Circ. 33413 and 33425;\nAstroSat CZTI detection: Navaneeth et al., GCN Circ. 33415;\nGRBAlpha detection: Dafcikova et al., GCN Circ. 33418;\nVZLUSAT-2 detection: Ripa et al., GCN Circ. 33424)\ntriggered Konus-Wind at T0=56645.615 s UT (15:44:05.615).\n\nThe burst light curve shows a multipeaked structure\nwhich starts at ~T0 and has a total duration of ~196 s.\nThe emission is seen up to ~10 MeV.\n\nThe Konus-Wind light curve of this GRB is available at\nhttp://www.ioffe.ru/LEA/GRBs/GRB230307_T56645/\n\nAs observed by Konus-Wind, the burst\nhad a fluence of 3.58(-0.08,+0.08)x10^-3 erg/cm2,\nand a 64-ms peak flux, measured from T0+6.224 s,\nof 6.66(-0.42,+0.46)x10^-4 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+71.424 s)\nis best fit in the 530 keV - 10 MeV range\nby a power law with exponential cutoff model:\ndN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)\nwith  alpha = -0.60(-0.08,+0.08)\nand Ep = 1000(-16,+15) keV (chi2 = 41/42 dof).\nFitting by a GRB (Band) model yields the same alpha and Ep,\nand an upper limit on the high energy photon index: beta < -5.4\n(chi2 = 41/41 dof).\n\nThe spectrum near the maximum count rate\n(measured from T0+6.144 to T0+6.400 s)\nis best fit in the 530 keV - 10 MeV range\nby a power law with exponential cutoff model:\nwith  alpha = -0.13(-0.31,+0.35)\nand Ep = 1321(-62,+60) keV (chi2 = 19/21 dof).\nFitting by a GRB (Band) model yields the same alpha and Ep,\nand an upper limit on the high energy photon index: beta < -4.3\n(chi2 = 19/20 dof).\n\nThe energy fluence of the burst is the second highest\n(after BOAT GRB 221009A) and the energy peak flux is the 5th highest \nobserved for GRBs for almost 28 years of the KW operation.\nThis supports the results reported in Burns et al., GCN Circ. 33414.\n\nAll the quoted errors are at the 90% confidence level.\nAll the quoted values are preliminary.",
  "circularId": 33427,
  "createdOn": 1678312247000,
  "email": "svinkin@mail.ioffe.ru",
  "subject": "Konus-Wind detection of GRB 230307A",
  "submitter": "Dmitry Svinkin at Ioffe Institute  <svinkin@mail.ioffe.ru>",
  "eventId": "GRB 230307A"
}