{
  "bibcode": "2025GCN.39978....1S",
  "circularId": 39978,
  "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 250327B\n(SVOM-ECLAIRs detection: Bouchet et al., GCN 39888)\nwas detected by Konus-Wind (KW) in the waiting mode\nat T0 = T0(ECLAIRs) = 76287 s UT (21:11:27).\n\nA Bayesian block analysis of the KW  waiting mode data\nin the 20-1200 keV band reveals a ~20 sigma count rate\nincrease in the interval from ~T0-12 s to ~T0+424 s.\n\nThe Konus-Wind light curve of this GRB is available at\nhttp://www.ioffe.ru/LEA/GRBs/GRB250327B/\n\nThe total burst fluence is 2.31(-0.22,+0.26)x10^-5 erg/cm^2,\nand the 2.944 s peak energy flux, measured from T0+85 s,\nis 2.43(-0.52,+0.55)x10^-7 erg/cm^2.\n(both in the 20 keV - 10 MeV energy range).\n\nThe time-integrated spectrum of the burst,\nmeasured from T0-12 s to T0+424 s,\ncan be described by a power law with exponential cutoff (CPL) model\ndN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)\nwith alpha = -1.11(-0.17,+0.21) and Ep = 212(-38,+48) keV.\n\nThe spectrum near the peak count rate, measured from T0+76 s to T0+91 s,\ncan be described by a CPL model with\nalpha = -0.82(-0.31,+0.43) and Ep = 203(-49,+64) keV.\n\nAssuming the redshift z=3.035 (Malesani et al., GCN 39893)\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 4.78(-0.45,+0.54)x10^53 erg,\nthe peak luminosity L_iso is 2.03(-0.44,+0.46)x10^52 erg/s,\nthe rest-frame peak energy of the time-averaged spectrum Ep,i,z is 856(-152,+195) keV and \nthe spectrum near the maximum count rate Ep,p,z is 818(-198,+257) keV.\n\nWith the obtained estimates, GRB 250327B is inside 68% prediction band for the 'Amati' and \n90% prediction band for the 'Yonetoku' relations derived for the sample of >300 long KW GRBs \nwith known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021),\nsee http://www.ioffe.ru/LEA/GRBs/GRB250327B/GRB250327B_rest_frame.pdf\n\nAll the quoted errors are estimated at the 68% confidence level.\nAll the presented results are preliminary. ",
  "createdOn": 1743439241843,
  "submitter": "Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>",
  "eventId": "GRB 250327B",
  "format": "text/plain",
  "subject": " Konus-Wind detection of GRB 250327B",
  "submittedHow": "web"
}