TITLE:   GCN CIRCULAR
NUMBER:  40384
SUBJECT: GRB 250430A / EP250430a: AstroSat CZTI detection
DATE:    25/05/07 15:16:23 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 the long duration GRB 250430A which was also detected by Swift/BAT (Moss et al., GCN Circ. 40356), Konus/Wind (Svinkin et al., GCN Circ. 40367), and associated with the detection of EP250430a by EP/WXT (Wang et al., GCN Circ. 40299).

The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-04-30 17:31:00.84 UTC. The measured peak count rate associated with the burst is 279 (+66, -70) counts/s above the background in the combined data of all quadrants, with a total of 761 (+210, -232) counts. The local mean background count rate was 1336 (+7, -8) counts/s. We measure a T90 of 7.1 (+0.5, -2.5) 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