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GCN Circular 34677

Subject
GRB 230911B: AstroSat CZTI detection
Date
2023-09-12T13:29:01Z (7 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 the long-duration GRB 230911B which was also detected by Fermi-GBM (Fermi GBM team, GCN Circ. 34653) along with GRBAlpha and VZLUSAT-2 (Dafcikova et al., GCN Circ. 34664).

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2023-09-11 04:25:51.50 UTC. The measured peak count rate associated with the burst is 467 (+56, -35) counts/s above the background in the combined data of all quadrants, with a total of 3390 (+378, -416) counts. The local mean background count rate was 593 (+4, -4) counts/s. Using cumulative rates, we measure a T90 of 15 (+5, -3) 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 2023-09-11 04:25:51.83 UTC. The measured peak count rate associated with the burst is 790 (+75, -76) counts/s above the background in the combined data of all quadrants, with a total of 4781 (+532, -605) counts. The local mean background count rate was 1400 (+6, -7) counts/s. We measure a T90 of 14 (+7, -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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