{
  "subject": "Konus-Wind detection of GRB 250919A",
  "editedBy": "Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Dmitry Frederiks at Ioffe Institute <ddfrederiks@gmail.com>",
  "circularId": 41905,
  "createdOn": 1758383437124,
  "editedOn": 1758505747694,
  "submitter": "Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>",
  "eventId": "GRB 250919A",
  "version": 2,
  "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\nThe long GRB 250919A (Fermi-GBM detection:\nThe Fermi GBM team, GCN 41874; Mukherjee & Meegan, GCN 41890;\nEP-WXT detection: Liang et al., GCN 41879;\nSVOM-GRM observaion: Wang et al., GCN 41882),\nFermi-LAT detection: Holzmann Airasca et al., GCN 41884;\nGlowbug detection: Cheung et al., GCN 41891)\ntriggered Konus-Wind (KW) at T0=1741.403 s UT (00:29:01.403).\n\nThe burst consists of two separated emission pulses\nand had the total duration of ~240 s.\nThe emission is seen up to ~10 MeV.\n\nThe Konus-Wind light curve of this GRB is available at\nhttp://www.ioffe.ru/LEA/GRBs/GRB250919_T01741/\n\nAs observed by Konus-Wind, the burst had\na fluence of (4.24 ± 0.25)x10^-4 erg/cm^2 and\na 64-ms peak energy flux, measured from T0 + 23.168 s,\nof (1.33 ± 0.09)x10^-4 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).\n\nThe time-integrated spectrum (measured from T0 to T0+218 s)\nis best fit in the 20 keV - 15 MeV range by a GRB (Band) function\nwith the following model parameters:\nthe low-energy photon index alpha = -0.94 (-0.05,+0.05),\nthe high energy photon index beta = -2.32 (-0.17,+0.11),\nthe peak energy Ep = 452 (-33,+39) keV,\nchi2 = 101/97 dof.\n\nThe spectrum near the peak count rate (measured from T0+23.04 to T0+23.296 s)\nis best fit in the 20 keV - 15 MeV range by a GRB (Band) function\nwith the following model parameters:\nthe low-energy photon index alpha = -0.07 (-0.09,+0.10),\nthe high energy photon index beta = -2.15 (-0.07,+0.06),\nthe peak energy Ep = 515 (-38,+42) keV,\nchi2 = 63/62 dof.\n\nAssuming the redshift z=1.145 (Levan et al., GCN 41883)\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 (1.53 ± 0.09)x10^54 erg,\nthe isotropic peak luminosity L_iso to (1.03 ± 0.07)x10^54 erg/s, and\nthe rest-frame peak spectral energy Ep,z to (970 ± 80) keV.\nWith the obtained estimates, GRB 250919A is consistent with 68% prediction bands\nof both 'Amati' and 'Yonetoku' relations 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/GRB250919_T01741/GRB250919A_rest_frame.pdf\n\nAll the quoted errors are estimated at the 68% confidence level.\nAll the presented results are preliminary.\n",
  "submittedHow": "email",
  "bibcode": "2025GCN.41905....1F",
  "format": "text/plain"
}