TITLE:   GCN CIRCULAR
NUMBER:  40142
SUBJECT: GRB 250412A: AstroSat CZTI detection
DATE:    25/04/14 06:02:43 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 250412A which was also detected by Fermi GBM (Trigger Num. 766173972).

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-04-12 18:06:07.50 UTC. The measured peak count rate associated with the burst is 109 (+29, -26) counts/s above the background in the combined data of three quadrants (out of four), with a total of 411 (+108, -138) counts. The local mean background count rate was 204 (+3, -4) counts/s. Using cumulative rates, we measure a T90 of 6.9 (+2.1, -2.9) s.

The source was also faintly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-04-12 18:06:08 UTC. The measured peak count rate associated with the burst is 219 (+64, -53) counts/s above the background in the combined data of all quadrants, with a total of 768 (+244, -251) counts. The local mean background count rate was 1231 (+6, -7) counts/s. We cannot reliably estimate the T90 for this GRB in the veto detector data.

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