{
  "bibcode": "2021GCN.30780....1F",
  "body": "D. Frederiks, S. Golenetskii, A.Lysenko, D. Svinkin,\nA. Ridnaya, A. Tsvetkova,  M. Ulanov, and T. Cline, report:\n\nThe long GRB GRB 210905A (Swift-BAT detection: Sonbas et al., GCN 30765;\nFermi GBM Sub-Threshold Detection: Veres & Roberts, GCN 30779),\nT0 (BAT) = 00:12:41, was detected by Konus-Wind (KW) in the waiting mode.\n\nA Bayesian block analysis of the KW waiting mode data in reveals\ntwo major emission episodes, separated by ~750 s.\nThe first episode, from ~T0-25.5s to ~t0+13 s, corresponds to the BAT and GBM detections;\nand the second episode, from ~T0-750 s to ~t0+870 s, corresponds to a bright flare visible\nin the XRT light curve (https://www.swift.ac.uk/xrt_curves/01071993/ ).\n\nThe KW light curve of this burst is available\nat http://www.ioffe.ru/LEA/GRBs/GRB210905A/\n\nModeling the KW 3-channel spectrum of the first episode\nby a power law with exponential cutoff (CPL) model\ndN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)\nyields alpha = -1.45 (-0.24, + 0.38) and Ep = 203 (-58,+111) keV.\nThe spectrum of the second episode can be described by a CPL\nwith alpha = -0.88 (-0.30, + 0.76) and Ep = 167 (-61,+88) keV.\n\nIn the 10 keV -10 MeV band, standard for the KW analysis,\nthe total burst fluence is (1.7 �� 0.7)x10^-5 erg/cm^2,\nand the 2.944 s peak energy flux is (3.6 �� 0.7)x10^-7 erg/cm^2.\n\nAssuming the redshift z=6.318 (Tanvir et al., GCN 30771)\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 isotropic energy release E_iso to ~1.1x10^54 erg,\nthe isotropic luminosity L_iso to ~1.7x10^53 erg/s,\nand the rest-frame peak energy of the time-integrated spectrum Ep,z to ~1300 keV.\nWith these values, GRB 210905A lies within 68% prediction bands for\nfor both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs\nwith known redshifts (Tsvetkova et al., 2021, ApJ, 908, 83),\nsee http://www.ioffe.ru/LEA/GRBs/GRB210905A/GRB210905A_rest_frame.pdf\n\nAll the quoted errors are estimated at the 68% confidence level.\nAll the presented results are preliminary.",
  "circularId": 30780,
  "createdOn": 1630940913000,
  "email": "fred@mail.ioffe.ru",
  "subject": "Konus-Wind detection of GRB 210905A",
  "submitter": "Dmitry Frederiks at Ioffe Institute  <fred@mail.ioffe.ru>",
  "eventId": "GRB 210905A"
}