GCN Circular 42008
Subject
GRB 250926A: AstroSat CZTI detection
Event
Date
2025-09-26T18:53:22Z (6 days ago)
From
Gaurav Waratkar at Caltech <gauravwaratkar@iitb.ac.in>
Via
Web form
A. Goyal (IITB), A. Arya (IITB), S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), Harsha K. H. (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 GRB 250926A which was also detected by Fermi/GBM (GCN Circ. 41993).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-09-26 00:21:21.75 UTC. The measured peak count rate associated with the burst is 739 (+163, -167) counts/s above the background in the combined data of all four quadrants, with a total of 396 (+100, -119) counts. The local mean background count rate was 265 (+15, -17) counts/s. Using cumulative rates, we measure a T90 of 1.5 (+0.3, -0.7) s.
The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-09-26 00:21:21.04 UTC. The measured peak count rate associated with the burst is 763 (+72, -74) counts/s above the background in the combined data of all quadrants, with a total of 891 (+229, -239) counts. The local mean background count rate was 1162 (+8, -9) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 from it.
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