GCN Circular 44933

S.Salunke (IUCAA), Harsha K. H. (IUCAA), A. Goyal (IITB), A. Arya (IITB), 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 long-duration GRB 260603C.

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  2026-06-03 20:22:40.3. The measured peak count rate associated with the burst is 83 (+25, -18) counts/s above the background in the combined data of two quadrants (out of four), with a total of 1141 (+467, -343) counts. The local mean background count rate was 150 (+0.7, -2) counts/s. We measure a T90 of 71 (+25, -13) s from the cumulative CZT light curve.

The source was faintly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve, with a single burst of emission, peaks at 2026-06-03 20:22:40.2. The measured peak count rate associated with the burst is 250 (+71, -36) counts/s above the background in the combined data of all quadrants, with a total of 822 (+283, -302) counts. The local mean background count rate was 1204 (+8, -8) counts/s. We measure a T90 of 5 (+4, -2) s from the cumulative Veto light curve, much lower than the T90 estimated in CZT detectors. We attribute this to a likely unfavorable angle from the boresight for Veto detectors. 

CZTI data products like interactive and downloadable light curves for this GRB can be found at: http://astrosat.iucaa.in/cift/cift_products/518214162.17/S518214162.17_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