TITLE:   GCN CIRCULAR
NUMBER:  36989
SUBJECT: GRB 240731A: AstroSat CZTI detection
DATE:    24/07/31 19:41:44 GMT
FROM:    Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>

S. Srijan (IITB), A. Dasgupta (BITS Pilani, Hyderabad), G. Waratkar (IITB), J. Joshi (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 GRB 240731A which was also detected by Fermi/GBM (Trigger 744128417) and INTEGRAL/SPI-ACS (Trigger 10826).

The source was detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2024-07-31 14:20:13.3 UTC. The measured peak count rate is 364 (+70, -74) counts/s above the background in the combined Veto data of all quadrants, with a total of 672 (+315, -330) counts. The local mean background count rate was 1305 (+13, -14) counts/s. We measure a T90 of 3.4 (+2.9, -2.4) 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