TITLE: GCN CIRCULAR NUMBER: 40077 SUBJECT: GRB 250403A: AstroSat CZTI detection DATE: 25/04/05 10:38:20 GMT FROM: Gaurav Waratkar at IIT Bombay gauravwaratkar@iitb.ac.in
M. Tembhurnikar (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 CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long duration GRB 250403A which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 40025) and SVOM/ECLAIRs (Y. Julakanti et. al. GCN Circ. 40026).
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-04-03 15:15:26.00 UTC. The measured peak count rate associated with the burst is 80 (+18, -23) counts/s above the background in the combined data of three quadrants (out of four), with a total of 343 (+110, -184) counts. The local mean background count rate was 225 (+3, -2) counts/s. Using cumulative rates, we measure a T90 of 9.1 (+1.3, -5.5) s.
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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