{
  "subject": "Konus-Wind detection of GRB 251118C (EP251118a)",
  "editedBy": "Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov>",
  "editedOn": 1763674864041,
  "eventId": "GRB 251118C",
  "submitter": "Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>",
  "circularId": 42765,
  "bibcode": "2025GCN.42765....1F",
  "body": "D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin,\nA. Tsvetkova,  M. Ulanov, and T. Cline,\non behalf of the Konus-Wind team, report:\n\nA long-duration GRB 251118C was detected by Konus-Wind (KW)\nin the waiting mode at T0=T0(KW)~16:44:49 UT.\nA Bayesian block analysis of the KW data in the 20-1500 keV\nband reveals a ~17 sigma count rate increase in the interval\nfrom ~T0-0.5 s to ~T0+23 s.\n\nCorrected for the propagation time, the burst started ~140 s\nafter the start time of the fast X-ray transient EP251118a\n(T0(EP)=16:42:29 UT; Jiang et al., GCN 42749).\nThe burst source is located in the southern ecliptic hemisphere\nat a low ecliptic latitude, which is consistent with the EP251118a localization.\nThe positional and temporal coincidence of GRB 251118C with\nthe EP251118a supports the conclusion that both events have\na common origin.\n\nThe Konus-Wind light curve of this GRB is available at\nhttp://www.ioffe.ru/LEA/GRBs/GRB251118C/\n\nThe time-integrated spectrum of the burst, measured from T0-0.5 s to T0+23 s,\ncan be described by a simple power function with the photon index (2.29 ± 0.11).\n\nThe total burst fluence is (5.08 ± 0.40)x10^-6 erg/cm^2,\nand the 2.944 s peak energy flux, measured from T0-1.96 s,\nis (4.84 ± 0.38)x10^-7 erg/cm^2(both in the 20 - 1500 keV energy range).\n\nAssuming the redshift z=1.216 (An et al., GCN 42756)\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 burst isotropic energy release E_iso to (2.06 ± 0.16)x10^52 erg,\nthe isotropic peak luminosity L_iso to (4.34 ± 0.34)x10^51 erg/s.\n\nAll the quoted errors are estimated at the 68% confidence level.\nAll the presented results are preliminary.",
  "version": 3,
  "format": "text/plain",
  "submittedHow": "email",
  "createdOn": 1763571531277
}