GCN Circular 45859
Subject
GRB 261007A / EP261007a: AstroSat CZTI detection
Event
Date
2026-10-08T13:11:37Z (6 hours ago)
Edited On
2026-10-08T14:35:18Z (4 hours ago)
From
ABHINAV GOYAL at Indian Institute of Technology Bombay <abhigoyale2003@gmail.com>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of ABHINAV GOYAL at Indian Institute of Technology Bombay <abhigoyale2003@gmail.com>
Via
Web form
Harsha K. H. (IUCAA), S. Salunke (IUCAA), S. Puri (IITB), A. Goyal (IITB), A. Arya (IITB), 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 261007A which was also detected by Fermi (Fermi GBM team, GCN Circ. 45830), SVOM/ECLAIRs (Goto et. al., GCN Circ. 45824), associated with EP261007a detected by Einstein Probe (Wen et. al., GCN Circ. 45828), and NuSTAR (Waratkar et. al., GCN Circ. 45846).
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 2026-10-07 05:40:02.36 UTC. The measured peak count rate associated with the burst is 1427 (+79, -36) counts/s above the background in the combined data of all quadrants, with a total of 15823 (+333, -396) counts. The local mean background count rate was 307 (+3, -3) counts/s. We measure a T90 of 22.9 (+0.3, -0.4) s from the cumulative CZT light curve.
The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2026-10-07 05:40:11.67 UTC. The measured peak count rate associated with the burst is 2125 (+88, -77) counts/s above the background in the combined data of all quadrants, with a total of 21607 (+536, -496) counts. The local mean background count rate was 772 (+6, -5) counts/s. We measure a T90 of 22.4 (+0.3, -0.3) s from the cumulative Veto light curve.
In the preliminary analysis, we find 1822 Compton events associated with this event.
CZTI data products like interactive and downloadable light curves for this GRB can be found at:
https://astrosat.iucaa.in/cift/cift_products/ET20261007T053949/ET20261007T053949_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