GCN Circular 36001

J. Joshi (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 short-duration GRB 240324A. Inspection of INTEGRAL/SPI-ACS data also showed the detection of the burst.

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2024-03-24 03:35:14.25 UTC. The measured peak count rate associated with the burst is 365 (+162, -42) counts/s above the background in the combined data of all quadrants, with a total of 207 (+60, -59) counts. The local mean background count rate was 360 (+12, -14) counts/s. Using cumulative rates, we measure a T90 of 0.79 (+0.29, -0.27) 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 2024-03-24 03:35:13.39 UTC. The measured peak count rate associated with the burst is 660 (+79, -86) counts/s above the background in the combined data of all quadrants, with a total of 1191 (+246, -255) counts. The local mean background count rate was 1665 (+9, -10) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 from it.

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