GCN Circular 44996
Subject
GRB 260616A: AstroSat CZTI detection
Event
Date
2026-06-19T11:50:15Z (21 days ago)
From
Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com>
Via
Web form
S.Salunke(IUCAA), Utkarsh Pathak(IITB), A. Goyal (IITB), A. Arya (IITB), Harsha K. H. (IUCAA), G. Waratkar (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 ML pipeline (Abraham et al., 2021, MNRAS, 504, 3084) and the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long, bright GRB 260616A which was also detected by Fermi/GBM (Fermi GBM team, GCN Circ. 44948), Fermi/LAT (S. Lopez et al., GCN Circ. 44960), GECAM-B (Hao-Xuan Guo et al., GCN Circ. 44964), Konus-Wind (A. Ridnaia et al., GCN Circ. 44967), Insight HXMT (Chen-Wei Wang et al., GCN Circ. 44980), NuSTAR(G. Waratkar et al., 44987).
The source was clearly 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 2026-06-16 03:22:46.024. The measured peak count rate associated with the burst is 241 (+20, -9) counts/s above the background in the combined data of three quadrants (out of four), with a total of 16061 (+515, -588) counts. The local mean background count rate was 203 (+1, -2) counts/s. We measure a T90 of 113 (+5, -5) 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 showed multiple peaks of emission with the strongest peak at 2026-06-16 03:22:44.598. The measured peak count rate associated with the burst is 724 (+35, -35) counts/s above the background in the combined data of all quadrants, with a total of 45925.00 (+1118, -1178) counts.
The local mean background count rate was 1290 (+2, -3) counts/s. We measure a T90 of 112 (+3, -4) s from the cumulative Veto light curve.
In the preliminary analysis, we find 2989 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/ET20260616T032154/ET20260616T032154_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