GCN Circular 35197

P. K. Navaneeth (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 231127A which was also detected by CALET (Trigger Num. 1385097164).

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2023-11-27 05:14:21.75 UTC. The measured peak count rate associated with the burst is 433 (+159, -60) counts/s above the background in the combined data of all quadrants, with a total of 571 (+157, -130) counts. The local mean background count rate was 325 (+7, -11) counts/s. Using cumulative rates, we measure a T90 of 3.0 (+1.4, -0.8) s.

The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2023-11-27 05:14:21.69 UTC. The measured peak count rate associated with the burst is 822 (+78, -76) counts/s above the background in the combined data of all quadrants, with a total of 2145 (+310, -342) counts. The local mean background count rate was 1452 (+11, -12) counts/s. We measure a T90 of 5 (+2, -3) s from the cumulative Veto light curve. We note that this T90 measurement has higher uncertainty due to the intrinsic 1 s binning of Veto 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