TITLE:   GCN CIRCULAR
NUMBER:  36957
SUBJECT: GRB 240727C: AstroSat CZTI detection of a long burst
DATE:    24/07/27 22:57:07 GMT
FROM:    Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>

A. Dasgupta (BITS Pilani, Hyderabad), S. Srijan (IITB), 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 a long-duration GRB 240727C which was also detected by INTEGRAL/SPI-ACS (Trigger 10817).

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2024-07-27 17:30:08.2 UTC. The measured peak count rate associated with the burst is 280 (+160, -1) counts/s above the background in the combined data of all quadrants, with a total of 635 (+187, -160) counts. The local mean background count rate was 338 (+4, -8) counts/s. Using cumulative rates, we measure a T90 of 7.0 (+1.0, -2.4) s.

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2024-07-27 17:30:07.7 UTC. The measured peak count rate is 376 (+63, -61) counts/s above the background in the combined Veto data of three quadrants (out of four), with a total of 1084 (+274, -282) counts. The local mean background count rate was 1079 (+7, -9) counts/s. We measure a T90 of 5.7 (+2.7, -3.0) 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