TITLE: GCN CIRCULAR NUMBER: 6403 SUBJECT: Konus-Wind and Konus-A observation of GRB 070508 DATE: 07/05/10 14:54:51 GMT FROM: Valentin Pal'shin at Ioffe Inst S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, P. Oleynik, M. Ulanov and T. Cline on behalf of the Konus-Wind and Konus-A teams report: The long bright GRB 070508 (Swift-BAT trigger #278854: Grupe et al., GCN 6383; Barthelmy et al., GCN 6390), triggered Konus-Wind at T0=15502.779 s UT (04:18:22.779). This burst also triggered Konus-A at T0=15503.790 s UT (04:18:23.790) The burst started at T-T0 ~-13 s and had a duration of ~40 s. As observed by Konus-Wind the burst had a fluence of 3.97(-0.23, +0.07)x10^-5 erg/cm2, and a 64-ms peak flux measured from T0+8.832 s 8.30(-1.11, +1.03)x10^-6 erg/cm2/s (both in the 20 keV - 1 MeV energy range). The burst shows strong spectral evolution. The time-integrated spectrum of the burst (from T0 to T0+27.904 s) can be fitted (in the 25 keV - 1 MeV range) by a power law with exponential cutoff model: dN/dE ~ E^(-alpha)*exp(-E*(2-alpha)/Ep) with alpha = 0.81 +/- 0.07 and Ep = 188 +/- 8 keV (chi2 = 65/52 dof). Assuming z = 0.82 (Jakobsson et al., GCN 6398) and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.3, Omega_\Lambda = 0.7, the isotropic bolometric energy release is E_iso ~7.0x10^52 erg, and the maximum bolometric luminosity is (L_iso)_max ~1.1x10^53 erg/s. All the quoted errors are at the 90% confidence level. The Konus-Wind light curve of this GRB is available at http://www.ioffe.rssi.ru/LEA/GRBs/GRB070508_T15502/