TITLE: GCN CIRCULAR NUMBER: 9833 SUBJECT: GRB 090820: detection of a strong burst by RT-2 on board CORONAS PHOTON DATE: 09/08/24 06:34:33 GMT FROM: Sandip K. Chakrabarti at S.N. Bose Nat. Centre for Basic Sci. GRB 090820: RT-2 detection of a strong burst S. K. Chakrabarti, A. Nandi, D. Debnath, T. C. Kotoch (ICSP, Kolkata, India), A. R. Rao, J. P. Malkar, M. K. Hingar, V. K. Agrawal (TIFR, Mumbai, India), T. R. Chidambaram, P. Vinod, S. Sreekumar (VSSC, Thiruvananthapuram, India), Y. D. Kotov, A. S. Buslov, V. N. Yurov, V. G. Tyshkevich, A. I. Arkhangelskij, R. A.Zyatkov (MephI, Moscow, Russia) report: The RT-2 Experiment onboard the CORONAS-PHOTON satellite has detected GRB 090820 (FERMI, Trigger No.- 272421498, V. Connaughton, GCN 9829) which is triggered at T0 = 00h 38m 16s (UT) (Onboard processor switch/toggle to Flare mode from Quiet mode). The satellite was in the GOOD/LIGHT mode with Earth latitude = -64.09 and longitude = 169.11. with GOOD time observation of 600 sec starting at 00h 29m 16sec (UT) and ending at 00h 39m 16sec (UT). After 30 sec, the satellite completely entered into BAD mode of high charge particle region. The GRB light curve shows a simple profile of a strong emission peak at T0+34 sec with a weak precursor (T0). The time duration of the brightest emission is around 19 sec with ~1100 cts/sec. Both RT-2/S and RT-2/G detectors have registered this burst profile in the energy band of 15 - 1000 keV with strongest emission in the energy range of above 100 keV to 330 keV. It is also noted that the burst width decreases with the increase in the energy band, a quite natural phenomena of GRB burst profile. This analysis is preliminary. Analysis of time resolved spectral data is going on, however the light curve is available at the web-site: http://csp.res.in/rt2_files/grb090820-lc.html