TITLE:   GCN CIRCULAR
NUMBER:  19867
SUBJECT: GRB160821A: Astrosat CZTI (veto) detection
DATE:    16/08/26 11:58:52 GMT
FROM:    Varun Bhalerao at IUCAA  <varunb@iucaa.in>

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

The bright long GRB160821A (Barthelmy et al., GCN Circ. 19830) was detected using the CsI veto detectors on Astrosat CZTI (Bhalerao et al., arXiv:1608.03408). The primary CZTI detectors were disabled as the satellite was passing through the South Atlantic Anomaly at that time.

The source was clearly detected in the 40-200 keV energy range. The light curve shows a single peak, with the strongest peak at 20:36:45.00 UT, 133 seconds after BAT Trigger at 20:34:28 UT. The time delay arises from detection of the main peak of the burst, and the timing is consistent with the Fermi LAT (McEnery et al., GCN 19831) and CALET (Marrocchesi et al., GCN 19865). The peak count rate in the CsI detectors was 11200 counts/sec above the background (four quadrants summed together), with a total of 149300 counts. The local mean background count rate was 1400 counts/sec. Using cumulative rates, we measure a T90 of 42 secs.

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.