GCN Circular 42591
Subject
GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
Event
Date
2025-11-05T18:10:53Z (2 days ago)
From
Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com>
Via
Web form
Harsha K. H. (IUCAA), S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), A. Goyal (IITB), A. Arya (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 251105B which was also detected by SVOM/GRM (Wang et. al., GCN Circ. 42586), Fermi/GBM (Hamburg et. al., GCN Circ. 42589) and Konus-Wind (IPN notices).
The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve shows an initial short-duration burst followed by an extended emission which peaks at 2025-11-05 00:58:56.35 UTC. The measured peak count rate associated with the burst is 253 (+94, -8) counts/s above the background in the combined data of all quadrants, with a total of 2711 (+723, -732) counts. The local mean background count rate was 1840 (+6, -6) counts/s. We measure a T90 of 24 (+11, -9) s from the cumulative Veto light curve for the entire burst.
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