GCN Circular 45687
Subject
GRB 260921A: AstroSat CZTI detection
Event
Date
2026-09-22T05:23:16Z (2 days ago)
From
Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com>
Via
Web form
A. Goyal (IITB), A. Arya (IITB), Harsha K. H. (IUCAA), S. Salunke(IUCAA), 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 GRB 260921A which was also detected by Fermi (Fermi GBM team, GCN Circ. 45674), Swift BAT (Parsotan et. al, GCN Circ. 45686).
The source was 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 2026-09-21 09:29:13.18 UTC. The measured peak count rate associated with the burst is 123 (+38, -16) counts/s above the background in the combined data of all quadrants, with a total of 551 (+257, -252) counts. The local mean background count rate was 307 (+2, -4) counts/s. Due to poor statistics, we cannot reliably estimate the T90 from it.
The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2026-09-21 09:29:10.55 UTC .The measured peak count rate associated with the burst is 563 (+55, -61) counts/s above the background in the combined data of all quadrants, with a total of 1892 (+187, -211) counts. The local mean background count rate was 682 (+4, -4) counts/s. We measure a T90 of 7 (+1, -2) s from the cumulative Veto light curve.
CZTI data products like interactive and downloadable light curves for this GRB can be found at: https://astrosat.iucaa.in/cift/cift_products/ET20260921T092910/ET20260921T092910_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