TITLE:   GCN CIRCULAR
NUMBER:  23436
SUBJECT: GRB 181020A: AstroSat CZTI detection
DATE:    18/11/23 14:34:19 GMT
FROM:    Vidushi Sharma at IUCAA  <vidushi@iucaa.in>

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

Analysis of AstroSat CZTI data showed the detection of a long GRB 181020A, which was also detected by Swift (Moss M. J. et al., GCN 23349, XRT: Goad M. R. et al., GCN 23351, BAT: Sakamoto T. et al., GCN 23357), Fermi (LAT: Axelsson M. et al., GCN 23350 and GBM: Veres P. et al., GCN 23352), and Konus-Wind (Tsvetkova A. et al., GCN 23363).

The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with strongest peak at 19:00:40.500 UT. The measured peak count rate is 1000 cts/s above the background in combined data of four quadrants, with a total of 8409 cts. The local mean background count rate was 513.8 cts/s. Using cumulative rates, we measure a T90 of 19.4 s. In preliminary analysis, we find that 749 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.

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.