GCN Circular 32969

R. Gopalakrishnan (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. 
Bhalerao (IITB), D. Bhattacharya (Ashoka University/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 GRB221121A which was 
also detected by Fermi GBM (GCN Circ. 32960
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 ).

The source was clearly detected in the 20-200 keV energy range. The 
light curve peaks at 2022-11-21 06:34:50.5 UTC. The measured peak count 
rate associated with the burst is 173 (+42, -40) counts/s above the 
background in the combined data of all quadrants, with a total of 1531 
(+490, -529) counts. The local mean background count rate was 532 (+3, 
-4) counts/s. Using cumulative rates, we measure a T90 of 22 (+15, -9) 
s.

It was also clearly detected in the CsI anticoincidence (Veto) detector 
in the 100-500 keV energy range. The light curve peaks at 2022-11-21 
06:34:53.9 UTC. The measured peak count rate is 283 (+79, -30) counts/s 
above the background in the combined Veto data of all quadrants, with a 
total of 3488 (+696, -662) counts. The local mean background count rate 
was 1746 (+6, -6) counts/s. We measure a T90 of 22 (+10, -4) 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, URSC, IUCAA, SAC, 
and PRL. The Indian Space Research Organisation funded, managed, and 
facilitated the project.