GCN Circular 33042

M. Dixit (IITB), G. Waratkar (IITB), R. Gopalakrishnan (IUCAA), 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 GRB 221208A which was also 
detected by KONUS-Wind and GECAM (both reported in GCN Notices).

The source was faintly detected with the CZT detectors in the 20-200 keV 
energy range. The light curve peaks at 2022-12-08 03:10:54.5 UTC. The 
measured peak count rate associated with the burst is 45.6 (+21.8, -8.6) 
counts/s above the background in the combined data of three quadrants, 
with a total of 184 (+103, -98) counts. The local mean background count 
rate was 102.5 (+1.3, -1.7) counts/s. Using cumulative rates, we measure 
a T90 of 6.86 (+4.20, -3.59) s.

It was also clearly detected in the CsI anticoincidence (Veto) detectors 
in the 100-500 keV energy range. The light curve peaks at 2022-12-08 
03:10:54.2 UTC. The measured peak count rate is 581.1 (+71.1, -76.6) 
counts/s above the background in the combined Veto data of all 
quadrants, with a total of 1622 (+380, -416) counts. The local mean 
background count rate was 1452.6 (+4.5, -5.2) counts/s. We measure a T90 
of 4.81 (+6.88, -2.38) 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.