TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3518 SUBJECT: Konus-Wind observation of GRB 050603 DATE: 05/06/04 15:44:05 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and T. Cline on behalf of the Konus-Wind team report: The long bright multipeak GRB 050603 (Swift-BAT trigger=131560: GCN 3509, 3512) triggered Konus-Wind at T0=23340.767 s UT (06:29:00.767). As observed by Konus-Wind it had a duration of ~6 s, fluence (3.41 ± 0.06)10-5 erg/cm2, peak flux on 16-ms time scale (3.2 ± 0.2)10-5 erg/cm2 s (both in the 20 keV - 3 MeV energy range). A weak decaying tail after the last, brigtest spike of the GRB is seen up to ~11 s after T0 (this tail was seen and repoted by Swift-BAT in GCN 3512). The time-integrated spectrum is well fitted by a GRB (Band) model: the low-energy photon index is alpha = -0.79 ± 0.06, the high energy photon index beta = -2.15 ± 0.09, the break energy E0 = 289 ± 36 keV, and the peak energy Ep = 349 ± 28 keV.