TITLE:   GCN CIRCULAR
NUMBER:  32017
SUBJECT: GRB 220507A: AstroSat CZTI detection
DATE:    22/05/11 03:23:31 GMT
FROM:    Gaurav Waratkar at IIT,Bombay  <gauravwaratkar@iitb.ac.in>

R. Gopalakrishnan (IUCAA), V. Prasad (IUCAA), G. Waratkar (IITB), A. 
Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao 
(IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat 
CZTI collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 
2021, JApA, 42, 73) showed the detection of a long GRB 220507A which was 
also detected by Fermi-GBM (GCN #32009).

The source was clearly detected in the 20-200 keV energy range. The 
light curve peaked at 2022-05-07 10:09:07.35 UT. The measured peak count 
rate associated with the burst is 466 (+188, -32) counts/s above the 
background in the combined data of three quadrants, with a total of 527 
(+145, -147) counts. The local mean background count rate was 366 (+7, 
-10) counts/s. Using cumulative rates, we measure a T90 of 5 (+1, -1) s.

It was also clearly detected in the CsI anticoincidence (Veto) detector 
in the 100-500 keV energy range. The light curve peaked at 2022-05-07 
10:09:07.21 UT. The measured peak count rate is 647 (+73, -81) counts/s 
above the background in the combined Veto data of four quadrants, with a 
total of 1796 (+412, -458) counts. The local mean background count rate 
was 1500 (+5, -6) counts/s. We measure a T90 of 6 (+11, -3) s from the 
cumulative Veto light curve.

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.