TITLE: GCN CIRCULAR NUMBER: 39714 SUBJECT: GRB 250313A: AstroSat CZTI detection of a bright long burst DATE: 25/03/14 03:34:39 GMT FROM: Gaurav Waratkar at IIT Bombay gauravwaratkar@iitb.ac.in
A. Dasgupta (BITS Pilani, Hyderabad), G. Waratkar (IITB), M. Tembhurnikar (IUCAA), 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 250313A which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 39703) and Fermi/LAT (Lalla et al., GCN Circ. 39711).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-03-13 14:34:39.0 UTC. The measured peak count rate associated with the burst is 1059 (+56, -49) counts/s above the background in the combined data of three quadrants (out of four), with a total of 6772 (+199, -209) counts. The local mean background count rate was 182 (+2, -3) counts/s. Using cumulative rates, we measure a T90 of 12 (+1, -1) s.
It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-03-13 14:34:42.3 UTC. The measured peak count rate is 2082 (+96, -75) counts/s above the background in the combined Veto data of all quadrants, with a total of 13178 (+422, -439) counts. The local mean background count rate was 1222 (+6, -7) counts/s. We measure a T90 of 10 (+1, -1) 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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