{
  "subject": "Konus-Wind detection of GRB 250424A",
  "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 GRB 250424A\n(Swift-BAT detection: Cenko et al., GCN 40224;\nAstroSat CZTI detection: Harsha et al., GCN 40231)\ntriggered Konus-Wind at T0=24733.431 s UT (06:52:13.431).\n\nThe burst light curve shows a single pulse\nwhich starts at ~T0-17.9 s and has a total duration of ~40.5 s.\nThe emission is seen up to ~2 MeV.\n\nThe Konus-Wind light curve of this GRB is available at\nhttp://www.ioffe.ru/LEA/GRBs/GRB250424_T24733/\n\nAs observed by Konus-Wind, the burst\nhad a fluence of 5.83(-0.16,+0.16)x10^-5 erg/cm2,\nand a 64-ms peak flux, measured from T0+4.192 s,\nof 8.88(-0.94,+0.95)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+21.760 s)\nis best fit in the 20 keV - 10 MeV range\nby the GRB (Band) model with the following parameters:\nthe low-energy photon index alpha = -1.30(-0.06,+0.06),\nthe high energy photon index beta = -2.87(-0.15,+0.11),\nthe peak energy Ep = 104(-3,+3) keV\n(chi2 = 94/82 dof).\n\nThe spectrum near the maximum count rate\n(measured from T0+0.256 to T0+5.376 s)\nis best fit in the 20 keV - 10 MeV range\nby the GRB (Band) model with the following parameters:\nthe low-energy photon index alpha = -1.09(-0.06,+0.07),\nthe high energy photon index beta = -2.91(-0.15,+0.12),\nthe peak energy Ep = 129(-4,+5) keV\n(chi2 = 72/66 dof).\n\nAssuming the redshift z=0.310 (Saccardi et al., GCN 40228)\nand a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,\nand Omega_Lambda = 0.685 (Planck Collaboration, 2014),\nwe estimate the following rest-frame parameters:\nthe isotropic energy release E_iso is 1.49(-0.04,+0.04)x10^52 erg,\nthe peak luminosity L_iso is 2.97(-0.31,+0.32)x10^51 erg/s,\nthe rest-frame peak energy of the time-averaged spectrum\nEp,i,z is 137(-4,+4) keV and the spectrum near the maximum count rate\nEp,p,z is 169(-5,+7) keV.\n\nWith the obtained estimates, GRB 250424A is inside 68% prediction bands for\nboth 'Amati' and 'Yonetoku' relations derived for the sample of >300 long\nKW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021),\nsee http://www.ioffe.ru/LEA/GRBs/GRB250424_T24733/GRB250424A_rest_frame.pdf\n\nAll the quoted errors are at the 68% confidence level.\nAll the quoted values are preliminary.",
  "format": "text/plain",
  "eventId": "GRB 250424A",
  "submittedHow": "web",
  "createdOn": 1745532757697,
  "circularId": 40243,
  "bibcode": "2025GCN.40243....1R",
  "submitter": "Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>"
}