[vsnet-grb-info 21467] GRB 181222A: AstroSat CZTI detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23566
SUBJECT: GRB 181222A: AstroSat CZTI detection
DATE:    18/12/27 09:35:44 GMT
FROM:    Vidushi Sharma at IUCAA  <vidushi at 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 long GRB 181222A, which was also detected by MAXI/GSC (Negoro H. et al., GCN 23547), Fermi/GBM (Veres P. et al., GCN 23548), CALET (Sakamoto T. et al., GCN 23553) and Konus-Wind (Kozlova A. et al., GCN 23559).

The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with strongest peak at 06:43:09.500 UT. The measured peak count rate is 1720 cts/s above the background in combined data of four quadrants, with a total of 14364 cts. The local mean background count rate was 522 cts/s. Using cumulative rates, we measure a T90 of 117 s. In preliminary analysis, we find that 1258 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.