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GCN Circular 35116

Subject
GRB 231118A: AstroSat CZTI detection
Date
2023-11-19T05:42:15Z (3 months ago)
From
Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>
Via
Web form
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 long-duration GRB 231118A which was also detected by Fermi-GBM (Fermi GBM team, GCN Circ. 35100), and Swift-BAT (Laha et al., GCN Circ. 35101).

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2023-11-18 17:16:33.55 UTC. The measured peak count rate associated with the burst is 773 (+165, -131) counts/s above the background in the combined data of three quadrants (out of four), with a total of 885 (+229, -215) counts. The local mean background count rate was 237 (+5, -8) counts/s. Using cumulative rates, we measure a T90 of 3.9 (+1.6, -1.0) 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 2023-11-18 17:16:32.74 UTC. The measured peak count rate associated with the burst is 638 (+71, -77) counts/s above the background in the combined data of all quadrants, with a total of 1634 (+436, -460) counts. The local mean background count rate was 1222 (+9, -10) counts/s. We measure a T90 of 3.7 (+1.8, -1.3) 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

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