GCN Circular 33201

G. Waratkar (IITB), A. Ahmad (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 GRB 230120A which was also 
detected by GECAM-B (TrigNum 135).

The source was clearly detected in the 20-200 keV energy range. The 
light curve showed multiple peaks of emission with the strongest peak at 
2023-01-20 10:53:13.5 UTC, followed by another strong peak about 100 s 
later. The measured peak count rate associated with the burst is 139.8 
(+28.1 -15.4) counts/s above the background in the combined data of all 
four quadrants, with a total of 1853 (+441 -318) counts. The local mean 
background count rate was 124.9 (+0.7 -1.2) counts/s. Using cumulative 
rates, we measure a T90 of 114.95 (+20.59 -8.86) s.

It was also clearly detected in the CsI anticoincidence (Veto) detector 
in the 100-500 keV energy range. The light curve showed multiple peaks 
of emission with the strongest strong peak at 2023-01-20 10:53:11.6 UTC, 
followed by another peak about 100 s later. The measured peak count rate 
is 778.6 (+73.8 -60.0) counts/s above the background in the combined 
Veto data of all four quadrants, with a total of 12139 (+1359 -1526) 
counts. The local mean background count rate was 1325.6 (+3.0 -3.3) 
counts/s. We measure a T90 of 120.35 (+11.00 -11.32) 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.