GCN Circular 36455

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 long-duration GRB 240513A which was also detected by Fermi (Trigger Num. 737277727).

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2024-05-13 07:22:02.65 UTC. The measured peak count rate associated with the burst is 648 (+161, -104) counts/s above the background in the combined data of three quadrants (out of four), with a total of 623 (+121, -101) counts. The local mean background count rate was 238 (+4, -7) counts/s. Using cumulative rates, we measure a T90 of 6.4 (+0.1, -0.4) s.

The source 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 peak at 2024-05-13 07:22:05.69 UTC. The measured peak count rate associated with the burst is 505 (+68, -73) counts/s above the background in the combined data of all quadrants, with a total of 1322 (+297, -319) counts. The local mean background count rate was 1255 (+6, -5) counts/s. We measure a T90 of 6.6 (+3.4, -3.4) 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