TITLE: GCN CIRCULAR NUMBER: 5685 SUBJECT: GRB 060928: RHESSI Spectral Fit DATE: 06/10/03 02:25:07 GMT FROM: Eric Bellm at UCB/SSL E. Bellm, M. Bandstra, S. Boggs, C. Wigger, W. Hajdas, D. M. Smith, and K. Hurley on behalf of the RHESSI team report: As observed by RHESSI, GRB060928 (Hurley et al., GCN 5684) displayed two periods of emission. The first had a duration of ~14s starting at about T0 = 01:17:05 UT. The preliminary fit to the time-integrated RHESSI spectrum from T0 - T0+14s between 500 keV and 10 MeV is simple power law with alpha = -2.21 +0.85/-1.74 (90% confidence levels). The 500 keV-10 MeV fluence is 1.5 E-5 erg/cm^2. The second outburst began at T1 = 01:20:05 UT and had a duration of ~25s. A spectral fit to the time-integrated RHESSI spectrum from T1 - T1+25s between 30 keV and 10 MeV gives a cutoff power law with alpha = -1.36 +0.05/-0.04 E0 = 2090 +480/-370 keV Epeak = 1340 +/- 220 keV The 30 keV-10 MeV fluence is 2.43 +/- 0.91 E-4 erg/cm^2.