TITLE:   GCN CIRCULAR
NUMBER:  21922
SUBJECT: GRB 170921B: AstroSat CZTI detection
DATE:    17/09/24 09:52:46 GMT
FROM:    Vidushi Sharma at IUCAA  <vidushi@iucaa.in>

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

Analysis of AstroSat CZTI data showed clear detection of short GRB 170921B (Fermi GBM detection: Bissaldi E. et al, GCN Circ. 21902) in the 40-200 keV energy range. The light curve shows a bright FRED-like emission with peak at 04:02:11.51 UT, coinciding with Fermi/GBM trigger. The measured peak count rate is 473.5 counts/s above the background in combined data of four quadrants, with a total 4475 counts. The local mean background count rate was 332 counts/s. Using cumulative rates, we measure a T90 of 30.5 s.

It was clearly detected in the CsI anticoincidence detector (Veto) also as bright detection 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.