TITLE:   GCN CIRCULAR
NUMBER:  20872
SUBJECT: GRB 170311B: AstroSat CZTI detection
DATE:    17/03/15 13:58:30 GMT
FROM:    Vidushi Sharma at IUCAA  <vidushi@iucaa.in>

V. Sharma and 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 GRB170311B (IPN Triangulation detection: K. Hurley et al., GCN Circ. 20859) in the 40-200 keV energy range. The light curve shows multiple peak structure with peak counts at 13:45:15.0 UT, ~10 s after Konus-Wind trigger (Konus-Wind observation: D. Frederiks et al., GCN Circ. 20865). For initial few seconds from the trigger time the light curve doesn't show excess counts above the background. The measured peak count rate is 412.9 counts/s above the background in combined data of four quadrants, with a total 1979 counts. The local mean background count rate was 378.1 counts/s. Using cumulative rates, we measure a T90 of 13.4 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.