GCN Circular 34645

P. K. Navaneeth (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 230908A which was also detected by CALET (Trigger Num. 1378226327).

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed a single burst of emission that peaked at 2023-09-08 16:41:22 UTC. The measured peak count rate associated with the burst is 447 (+173, -19) counts/s above the background in the combined data of three quadrants (out of four), with a total of 1458 (+285, -371) counts. The local mean background count rate was 327 (+5, -9) counts/s. Using cumulative rates, we measure a T90 of 9.5 (+3, -5) s.

The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed a single burst of emission that peaked at 2023-09-08 16:41:23 UTC. The measured peak count rate associated with the burst is 737 (+71, -75) counts/s above the background in the combined data of three quadrants (out of four), with a total of 4509 (+569, -583) counts. The local mean background count rate was 1096 (+7, -7) counts/s. We measure a T90 of 13 (+5, -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