TITLE: GCN CIRCULAR NUMBER: 42199 SUBJECT: GRB 251011A: AstroSat CZTI detection DATE: 25/10/11 09:26:10 GMT FROM: Anuraag Arya at IIT Bombay aryaanuraag910@gmail.com
M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), Harsha K. H. (IUCAA), A. Arya (IITB), A. Goyal (IITB), U. Pathak (IITB), G. Waratkar (Caltech/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 251011A which was also detected by Fermi GBM (GCN Circ. 42195).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-10-11 03:41:37.50 UTC. The measured peak count rate associated with the burst is 200 (+32, -29) counts/s above the background in the combined data three quadrants out of four, with a total of 743 (+117, -127) counts. The local mean background count rate was 208 (+3, -3) counts/s. Using cumulative rates, we measure a T90 of 6.5 (+2.1, -1.9) s.
The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed a peak of emission at 2025-10-11 03:41:37 UTC. The measured peak count rate associated with the burst is 356 (+68, -62) counts/s above the background in the combined data of all quadrants, with a total of 952 (+242, -256) counts. The local mean background count rate was 1335 (+7, -8) counts/s. We measure a T90 of 5.9 (+2.1, -2.9) 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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