GCN Circular 33493

P K. Navaneeth (IUCAA), 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 a long GRB 230321B which was 
also detected by Fermi GBM (TrigNum: 701058254) and KONUS-Wind.

The source was clearly detected in the 20-200 keV energy range. The 
light curve peaks at 2023-03-21 02:24:13.35 UTC. The measured peak count 
rate associated with the burst is 426 (+186, -1) counts/s above the 
background in the combined data of three quadrants (out of four), with a 
total of 1195 (+203, -204) counts. The local mean background count rate 
was 361 (+6, -8) counts/s. Using cumulative rates, we measure a T90 of 
5.57 (+2, -1) s.

The source was also clearly detected in the CsI anticoincidence (Veto) 
detector in the 100-500 keV energy range. The light curve peaks at 
2023-03-21 02:24:10.58 UTC. The measured peak count rate associated with 
the burst is 268 (+80, -39) counts/s above the background in the 
combined data of all quadrants, with a total of 1050 (+324, -377) 
counts. The local mean background count rate was 1568 (+6, -6) counts/s. 
We measure a T90 of 5.24 (+3, -2) s from the cumulative Veto light 
curve.

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.

CZTI GRB detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb