TITLE:   GCN CIRCULAR
NUMBER:  28589
SUBJECT: GRB 201009A: AstroSat CZTI detection
DATE:    20/10/09 10:48:43 GMT
FROM:    Soumya Gupta at IUCAA/ASTROSAT  <soumya@iucaa>

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 detection of a bright long GRB 201009A, which is also detected by AGILE (Ursi A. et al., GCN #28588).

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 2020-10-09 03:08:21.500 UT. The measured peak count rate associated with the burst is 4215 +/- 69 cts/s above the background in the combined data of four quadrants, with a total of 45310 +/- 77 cts. The local mean background count rate was 516 +/- 1 cts/s. Using cumulative rates, we measure a T90 of 40.20 +/- 0.13 s.  In a preliminary analysis, we find that 3509 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 2020-10-09 03:08:21.000 UT. The measured peak count rate is 12953 +/- 121 cts/s above the background in the combined Veto data of four quadrants, with a total of 71480 +/- 124 cts. The local mean background count rate was 1534 +/- 2  cts/s. We measure a T90 of 26.64 +/- 0.12 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.