GCN Circular 43109

A. Arya (IITB), A. Goyal (IITB), M. Tembhurnikar (IUCAA), S. Salunke (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 a long-duration GRB 251214D.

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-12-14 21:24:21.50 UTC. The measured peak count rate associated with the burst is 71 (+34, -11) counts/s above the background in the combined data of all quadrants, with a total of 576 (+192, -210) counts. The local mean background count rate was 264 (+3, -3) counts/s. Using cumulative rates, we measure a T90 of 16 (+3, -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 2025-12-14 21:24:21.75 UTC. The measured peak count rate associated with the burst is 231 (+68, -36) counts/s above the background in the combined data of all quadrants, with a total of 1844 (+413, -469) counts. The local mean background count rate was 1211 (+7, -7) counts/s. We measure a T90 of 20 (+2, -8) s from the cumulative Veto light curve.

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