GCN Circular 46040
Subject
GRB 261024D: AstroSat CZTI detection of a long burst
Event
Date
2026-10-26T10:14:30Z (6 days ago)
From
ABHINAV GOYAL at Indian Institute of Technology Bombay <abhigoyale2003@gmail.com>
Via
Web form
A. Goyal (IITB), A. Arya (IITB), S. Puri (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 261024D which was also detected by SVOM/GRM (via notices), and KONUS-Wind (via IPN notices).
The source was detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2026-10-24 21:33:06.85 UTC. The measured peak count rate associated with the burst is 105 (+28, -26) counts/s above the background in the combined data of three quadrants (out of four), with a total of 458 (+195, -196) counts. The local mean background count rate was 211 (+2, -2) counts/s. We measure a T90 of 11 (+7, -5) s from the cumulative CZT light curve. We caution that there is a 0.3 s dead time in the CZTI data just in the burst, hence the actual T90 may be slightly longer.
The source was also detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed a peak at 2026-10-24 21:33:06.86 UTC. The measured peak count rate associated with the burst is 405 (+49, -51) counts/s above the background in the combined data of three quadrants (out of four), with a total of 1698 (+303, -328) counts. The local mean background count rate was 520 (+3 -4) counts/s. We measure a T90 of 13 (+10, -5) 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/530573567.36/S530573567.36_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