{
  "bibcode": "2025GCN.39619....1S",
  "submitter": "Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>",
  "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 250306A\n(Swift-BAT detection: Evans et al., GCN 39606;\nAstrosat-CZTI detection: Tembhurnikar et al., GCN 39611)\ntriggered Konus-Wind at T0=59404.612 s UT (16:30:04.612).\n\nThe burst light curve shows a double-peaked structure\nwhich starts at ~T0-0.5 s and has a total duration of ~15 s.\nThe emission is seen up to ~3 MeV.\n\nThe Konus-Wind light curve of this GRB is available at\nhttp://www.ioffe.ru/LEA/GRBs/GRB250306_T59404/\n\nAs observed by Konus-Wind, the burst\nhad a fluence of 2.32(-0.15,+0.16)x10^-5 erg/cm2,\nand a 64-ms peak flux, measured from T0+1.120 s,\nof 1.40(-0.12,+0.12)x10^-5 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+18.176 s)\nis best fit in the 20 keV - 20 MeV range\nby the GRB (Band) model with the following parameters:\nthe low-energy photon index alpha = -0.94(-0.08,+0.08),\nthe high energy photon index beta = -2.78(-0.33,+0.19),\nthe peak energy Ep = 179(-10,+11) keV\n(chi2 = 84/97 dof).\n\nThe spectrum near the maximum count rate\n(measured from T0+0.256 to T0+1.792 s)\nis best fit in the 20 keV - 20 MeV range\nby the GRB (Band) model with the following parameters:\nthe low-energy photon index alpha = -0.62(-0.08,+0.09),\nthe high energy photon index beta = -2.59(-0.13,+0.10),\nthe peak energy Ep = 217(-13,+14) keV\n(chi2 = 55/54 dof).\n\nAll the quoted errors are at the 68% confidence level.\nAll the quoted values are preliminary.",
  "circularId": 39619,
  "eventId": "GRB 250306A",
  "submittedHow": "web",
  "format": "text/plain",
  "createdOn": 1741386619572,
  "subject": "Konus-Wind detection of GRB 250306A"
}