GCN Circular 28395

S. Gupta, V. Sharma 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 a weak detection of a short GRB 200907B, which was also detected by Swift (Beardmore A. et al., GCN #28384),  Swift-XRT (Evans P. et al., GCN #28385),  GROWTH-India optical (Kumar H. et al., GCN #28388), Global MASTER-Net (Lipunov V. et al., GCN #28392), and  MITSuME Okayama optical (Hosokawa R. et al., GCN #28393).

The source was clearly detected in the 40-200 keV energy range. The light curve showed a single peak of emission peaking at 2020-09-07 18:51:10.019 UT. The measured peak count rate associated with the burst is 160 +/- 24 cts/s above the background in the combined data of four quadrants, with a total of 259 +/- 3 cts. The local mean background count rate was 515+/- 1 cts/s. Using cumulative rates, we measure a T90 of 1.60 +/- 0.01 s.

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed a single peak of emission peaking at 2020-09-07 18:51:09.00 UT. The measured peak count rate is 513 +/- 44 cts/s above the background in the combined Veto data of four quadrants, with a total of 560 +/- 5 cts. The local mean background count rate was 1494 +/- 2 cts/s. We measure a T90 of 1.48 +/- 0.06 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.