TITLE: GCN CIRCULAR NUMBER: 43082 SUBJECT: EP251212a / GRB 251212A: AstroSat CZTI detection DATE: 25/12/13 07:55:15 GMT FROM: Gaurav Waratkar at Caltech gauravwaratkar@iitb.ac.in
S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), A. Arya (IITB), A. Goyal (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 GRB 251212A which was also detected by Konus-Wind (via IPN Notices), about 20 s after the trigger time of EP251212a detected by Einstein Probe / WXT (Yang et. al., GCN Circ. 43076).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-12-12 06:13:13.50 UTC. The measured peak count rate associated with the burst is 64 (+20, -21) counts/s above the background in the data of one quadrant (out of four), with a total of 136 (+55, -58) counts. The local mean background count rate was 83 (+2, -2) counts/s. Using cumulative rates, we measure a T90 of 5.6 (+0.6, -3.8) 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 2025-12-12 06:13:13.22 UTC. The measured peak count rate associated with the burst is 475 (+72, -74) counts/s above the background in the combined data of all quadrants, with a total of 1524 (+245, -269) counts. The local mean background count rate was 1568 (+7, -9) counts/s. We measure a T90 of 5.7 (+0.9, -1.9) 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
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