TITLE:   GCN CIRCULAR
NUMBER:  33400
SUBJECT: GRB 230304B: AstroSat CZTI detection
DATE:    23/03/06 06:39:48 GMT
FROM:    Gaurav Waratkar at IIT,Bombay  <gauravwaratkar@iitb.ac.in>

P K. Navaneeth (IUCAA), 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 GRB 230304B which was also 
detected by Fermi GBM (GCN Circ. 33396) and GRBAlpha (Dafcikova et al., 
GCN Circ. 33398).

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 
2023-03-04 14:35:49.5 UTC. The measured peak count rate associated with 
the burst is 640 (+51, -54) counts/s above the background in the 
combined data of three quadrants (out of four), with a total of 4194 
(+351, -404) counts. The local mean background count rate was 319 (+3, 
-5) counts/s. Using cumulative rates, we measure a T90 of 22.11 (+3, -4) 
s.

It was also clearly detected in the CsI anticoincidence (Veto) detector 
in the 100-500 keV energy range. The light curve peaks at 2023-03-04 
14:35:48.9 UTC. The measured peak count rate is 1900 (+90, -100) 
counts/s above the background in the combined Veto data of all 
quadrants, with a total of 12984 (+592, -623) counts. The local mean 
background count rate was 1314 (+7, -6) counts/s. We measure a T90 of 
20.5 (+2, -2) 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.