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GCN Circular 35692

Subject
GRB 240204A: AstroSat CZTI detection
Date
2024-02-06T14:39:17Z (4 months ago)
From
Varun Bhalerao at IIT Bombay <varunb@iitb.ac.in>
Via
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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 240204A which was also detected by Fermi-GBM (Fermi GBM Team, GCN Circ. 35664), and Swift (Cenko et al., GCN Circ. 35666).

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2024-02-04 15:07:49.50 UTC. The measured peak count rate associated with the burst is 201 (+40 -25) counts/s above the background in the combined data of four quadrants, with a total of 1125 (+193 -176) counts. The local mean background count rate was 308 (+5 -6) counts/s. Using cumulative rates, we measure a T90 of 10.5 (+1.1 -2.5) 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 2024-02-04 15:07:49.4 UTC. The measured peak count rate associated with the burst is 388 (+65, -60) counts/s above the background in the combined data of all quadrants, with a total of 2008 (+336, -351) counts. The local mean background count rate was 1276 (+6, -6) counts/s. We measure a T90 of 8.5 (+3.1, -2.1) 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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