GCN Circular 46005

A. Arya (IITB), S. Puri (IITB), A. Goyal (IITB), Harsha K. H. (IUCAA), S. Salunke (IUCAA), G. Waratkar (Caltech/IITB), V. Bhalerao (IITB),  A. Vibhute (IUCAA), 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 GRB 261020B.

The source was detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2026-10-20 14:52:41.55 UTC. The measured peak count rate associated with the burst is 1150 (+236, -249) counts/s above the background in the combined data of all quadrants, with a total of 108 (+30, -30) counts. The local mean background count rate was 267 (+12, -15) counts/s. We measure a T90 of 0.11 (+0.11, -0.03) s from the cumulative CZT light curve. 

The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2026-10-20 14:52:40.80 UTC. The measured peak count rate associated with the burst is 190 (+43, -44) counts/s above the background in the combined data of three quadrants (out of four), with a total of 132 (+107, -111) counts. The local mean background count rate was 458 (+7, -8) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 for our detection.

CZTI data products like interactive and downloadable light curves for this GRB can be found at: 
https://astrosat.iucaa.in/cift/cift_products/ET20261020T145241/ET20261020T145241_details.html

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