GCN Circular 28367

S. Gupta, V. Sharma, A. Vibhute and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (IUCAA/TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:

Analysis of AstroSat CZTI data showed the detection of a bright long GRB 200903E.

The source was clearly detected in the 40-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2020-09-03 02:34:50.40 UT. The measured peak count rate associated with the burst is 1061 +/- 38 cts/s above the background in the combined data of four quadrants, with a total of 22806 +/- 104 cts. The local mean background count rate was 597 +/- 1 cts/s. Using cumulative rates, we measure a T90 of 90.78 +/- 0.02 s. In preliminary analysis, we find that 1885 Compton events are associated with this event.

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2020-09-03 02:34:49.00 UT. The measured peak count rate is 3999 +/- 75 cts/s above the background in the combined Veto data of four quadrants, with a total of 79278 +/- 173 cts. The local mean background count rate was 1611 +/- 1 cts/s.  We measure a T90 of 90.50 +/- 0.03 s from the cumulative Veto light curve.

CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.