TITLE:   GCN CIRCULAR
NUMBER:  22694
SUBJECT: GRB 180427A: AstroSat CZTI detection
DATE:    18/05/09 13:34:15 GMT
FROM:    Vidushi Sharma at IUCAA  <vidushi@iucaa.in>

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:

Analysis of AstroSat CZTI data showed the detection of a bright GRB 180427A, which was also detected by Fermi-GBM (Bissaldi E. et al., GCN 22678), IPN Triangulation (Hurley K. et al., GCN 22679) and Konus-Wind (Kozlova A. et al., GCN 22680).

The source was clearly detected in the 40-200 keV energy range. The light curve shows a double-peaked structure in overall FRED-like emission, with strongest emission at 10:37:04.5 UT. The measured peak count rate is 1717 cts/s above the background in combined data of four quadrants, with a total of 18897 cts. The local mean background count rate was 494.8 cts/s. Using cumulative rates, we measure a T90 of 22.4 s. In Preliminary analysis, we find that 981.3 compton events are associated with this event.

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.