TITLE: GCN CIRCULAR NUMBER: 16445 SUBJECT: Konus-Wind observation of GRB 140621A DATE: 14/06/23 17:42:22 GMT FROM: Dmitry Svinkin at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lyssenko, and T. Cline on behalf of the Konus-Wind team, report: GRB 140621A (IPN triangulation: Golenetskii at al., GCN 16444) triggered Konus-Wind at T0=71407.498 s UT (19:50:07.498). The burst light curve shows a multipeak structure from ~T0-0.1 s to ~T0+6.2 s; the total duration of the burst is ~6.3 s. The emission is seen up to ~5 MeV. As observed by Konus-Wind, the burst had a fluence of 7.8(-1.8,+2.9)x10^-6 erg/cm2, and a 64-ms peak flux, measured from T0-0.064 s, of 5.6(-1.2,+1.3)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 15 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.11 (-0.24,+0.32), and Ep = 740(-260,+640) keV, chi2 = 82/98 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. The spectrum near the maximum count rate (measured from T0-0.064 to T0+0.064 s) is best fit in the 20 keV - 1.5 MeV range, by a power law with exponential cutoff model with alpha = -0.20(-0.35,+0.55), and Ep = 340(-80,+140) keV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB140621_T71407/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.