{
  "createdOn": 1700138631115,
  "subject": "Konus-Wind detection of GRB 231115A (a probable Magnetar Giant Flare from M82)",
  "submittedHow": "email-legacy",
  "circularId": 35062,
  "submitter": "Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>",
  "body": "D. Frederiks, D. Svinkin, A.Lysenko, A. Ridnaia,\nYu. Temiraev, A. Tsvetkova,  M. Ulanov, and T. Cline,\non behalf of the Konus-Wind team, report:\n\nThe short duration, hard spectrum GRB 231115A\n(Fermi GBM detection: Fermi GBM team GCN 35035, Dalessi et al. GCN 35044;\nINTEGRAL (IBAS) detection: Mereghetti et al., GCN 35037;\nGlowbug detection: Cheung et al., GCN 35045)\ntriggered Konus-Wind (KW) at T0= 56183.509 s UT (15:36:23.509).\n\nThe burst light curve shows a single FRED-like pulse,\nwhich starts, at ~T0-0.028 s with the fast (<4 ms) rise of\nthe emission intensity, which peaks at ~T0-0.016 s\nand has a total duration of ~66 ms.\n\nThe Konus-Wind light curve of this GRB is available at\nhttp://www.ioffe.ru/LEA/GRBs/GRB231115_T56183/\n\nAs observed by Konus-Wind, the burst had\na fluence of (7.3 ± 0.1)x10^-7 erg/cm^2 and\na 16-ms peak energy flux, measured from T0 - 0.018 s,\nof (2.2 ± 0.45)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).\n\nThe time-integrated spectrum (measured from T0-0.028 s to T0+0.036 s)\nis best fit in the 20 keV - 1.5 MeV range by a power law with exponential\ncutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)\nwith  alpha = 0.69(-0.54,+0.96) and Ep = 495(-77,+118) keV.\nA blackbody (BB) spectral model fits the spectrum equally well,\nwith the BB temperature kT = 114(-10,+9) keV.\n\nAssuming the likely GRB 231115A association with the nearby\nM82 galaxy at ~3.5 Mpc (D’Avanzo et al., GCN 35036;\nMereghetti et al., GCN 35037; Burns GCN 35038),\nwe estimate the burst isotropic energy Eiso to ~1.1x10^45 erg and\nthe 16-ms peak luminosity Liso to ~3.2x10^46 erg/s.\nThese values are in the range the of the energetics of initial pulses\nof magnetar giant flares (MGFs), which, assuming the short rise time\nand the hard energy spectrum of the burst, supports its MGF origin.\n\nAt 3.5 Mpc, the characteristic radius of the emission region,\nestimated from the KW blackbody spectral fit, is R~30 km,\nthe same order of magnitude as the radius of a neutron star or its magnetosphere.\n\nAll the quoted errors are estimated at the 68% confidence level.\nAll the presented results are preliminary.\n\n",
  "bibcode": "2023GCN.35062....1F",
  "eventId": "GRB 231115A"
}