{
  "bibcode": "2025GCN.39498....1R",
  "circularId": 39498,
  "submitter": "Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>",
  "submittedHow": "web",
  "eventId": "GRB 250225B",
  "format": "text/plain",
  "body": "A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin,\nA. Tsvetkova,  M. Ulanov, and T. Cline,\non behalf of the Konus-Wind team, report:\n\nThe long-duration GRB 250225B\n(Swift-BAT detection: Williams et al., GCN 39473;\nSVOM/GRM detection: Zhang et al., GCN 39493)\ntriggered Konus-Wind at T0=70750.895 s UT (19:39:10.895).\n\nThe burst light curve shows a bright initial pulse\nwhich starts at ~T0-2.2 s and has a total duration of ~3.3 s,\nfollowed by two weaker emission episodes centered\naround ~T0+60 s and T0+108 s.\nThe emission is seen up to ~6 MeV.\n\nThe Konus-Wind light curve of this GRB is available at\nhttp://www.ioffe.ru/LEA/GRBs/GRB250225_T70750/\n\nAs observed by Konus-Wind, the burst\nhad a fluence of 1.54(-0.18,+0.28)x10^-5 erg/cm2,\nand a 64-ms peak flux, measured from T0+0.262 s,\nof 1.14(-0.24,+0.35)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+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 = -1.14(-0.16,+0.18)\nand Ep = 634(-181,+393) keV (chi2 = 66/84 dof).\nFitting by a GRB (Band) model yields the same alpha and Ep,\nand an upper limit on the high energy photon index: beta < -1.7\n(chi2 = 66/83 dof).\n\nThe time-averaged spectrum of the second emission episode\n(measured from T0+57.600 to T0+65.792 s)\nis best fit in the 20 keV - 10 MeV range\nby a power law with exponential cutoff model\nwith alpha = -1.23(-0.21,+0.28)\nand Ep = 361(-118,+292) keV (chi2 = 97/99 dof).\nFitting by a GRB (Band) model yields the same alpha and Ep,\nand an upper limit on the high energy photon index: beta < -1.7\n(chi2 = 95/98 dof).\n\nThe time-averaged spectrum of the third emission episode\n(measured from T0+106.752 to T0+114.944 s)\nis best fit in the 20 keV - 10 MeV range\nby a power law with exponential cutoff model\nwith alpha = -0.91(-0.69,+1.12)\nand Ep = 187(-74,+228) keV (chi2 = 110/99 dof).\nFitting by a GRB (Band) model yields the same alpha and Ep,\nand an upper limit on the high energy photon index: beta < -1.7\n(chi2 = 110/98 dof).\n\nAll the quoted errors are at the 68% confidence level.\nAll the quoted values are preliminary.",
  "createdOn": 1740593640831,
  "subject": "Konus-Wind detection of GRB 250225B"
}