TITLE: GCN CIRCULAR NUMBER: 32783 SUBJECT: Konus-Wind detection of GRB 221016A DATE: 22/10/17 14:06:18 GMT FROM: Anna Ridnaia at Ioffe Institute ridnaia@mail.ioffe.ru
A.Ridnaia, D. Frederiks, A.Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report:
The long-duration GRB 221016A (Fermi-GBM detection: Fermi GBM team, GCN#32773, Bissaldi et al., GCN#32782; Swift-BAT detection: Page et al., GCN#32774) triggered Konus-Wind at T0=85166.713 s UT (23:39:26.713).
The burst light curve shows a single emission pulse which starts at ~T0-1.7 s and has a total duration of ~12.5 s. The emission is seen up to ~2 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB221016_T85166/
As observed by Konus-Wind, the burst had a fluence of 5.46(-0.74,+1.07)x10^-6 erg/cm2, and a 64-ms peak flux, measured from T0+0.800 s, of 1.87(-0.73,+0.74)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum of the burst (measured from T0 to T0+16.640 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.02(-0.33,+0.40) and Ep = 207(-46,+98) keV (chi2 = 60/99 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.0 (chi2 = 60/98 dof).
The spectrum near the maximum count rate (measured from T0+0.256 to T0+8.448 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model with alpha = -0.89(-0.30,+0.35) and Ep = 166(-26,+39) keV (chi2 = 81/96 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.4 (chi2 = 81/95 dof).
All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.