GCN Circular 21232

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

Routine on-ground analysis of AstroSat CZT Imager data showed the detection of a bright GRB 170607B, which was also detected by Fermi GBM (designation: bn170607946) at 2017-06-07 22:41:58.947 UT.

The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with the strongest peak at 22:42:04.947 UT, ~6 s after the Fermi Trigger. The measured peak count rate is 496.1 cts/s above the background in combined data of four quadrants, with a total of 7677 cts. The local mean background count rate was 354.9 cts/s. Using cumulative rates, we measure a T90 of 21.8 s.

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.