{
  "bibcode": "2025GCN.41508....1F",
  "circularId": 41508,
  "subject": "Konus-Wind detection of GRB 250821B",
  "submittedHow": "email",
  "createdOn": 1755965196161,
  "eventId": "GRB 250821B",
  "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 bright, long-duration GRB 250821B (Ferm-GBM detection:\nThe Fermi GBM team, GCN 41473; Smith and Meegan, GCN 41477;\nSVOM-GRM detection: Tan et al., GCN 41486;\nIPN localization Kozyrev et al., GCN 41498)\ntriggered Konus-Wind (KW) at T0=58069.135 s UT (16:07:49.135).\n\nThe burst light curve shows a single emission pulse with a total duration of ~2.5 s.\nThe emission is seen up to ~5 MeV.\n\nThe Konus-Wind light curve of this GRB is available at\nhttp://www.ioffe.ru/LEA/GRBs/GRB250821_T58069/\n\nAs observed by Konus-Wind, the burst had\na fluence of (1.34 ± 0.13)x10^-5 erg/cm^2 and\na 64-ms peak energy flux, measured from T0 + 0.512 s,\nof (1.77 ± 0.17)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).\n\nThe time-integrated spectrum (measured from T0 to T0+8.448 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 = -0.60 (-0.14,+0.15),\nthe high energy photon index beta = -2.24 (-0.13,+0.10),\nthe peak energy Ep = 193(-18,+21) keV,\nchi2 = 70/96 dof.\n\nAll the quoted errors are estimated at the 68% confidence level.\nAll the presented results are preliminary.\n",
  "submitter": "Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>"
}