GCN Circular 31179

V. Prasad (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao
(IITB), D. Bhattacharya (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 ML pipeline (Abraham et al.,
2021, MNRAS, 504, 3084) and CIFT framework (Sharma et al., 2021, JApA,
42, 73) showed the detection of a long GRB 211206B.  

The source was clearly detected in the 20-200 keV energy range. The
light curve showed multiple peaks of emission with the strongest peak at
2021-12-06 15:10:29.50 UT. The measured peak count rate associated with
the burst is 910 (+60, -65) cts/s above the background in the combined
data of two quadrants, with a total of 8746 (+348, -398) cts. The local
mean background count rate was 467 (+2, -2) cts/s. Using cumulative
rates, we measure a T90 of 27 (+1, -1) s. 

It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range. The light curve showed multiple peaks
of emission with the strongest peak at 2021-12-06 15:10:29.09 UT. The
measured peak count rate is 823 (+77, -80) cts/s above the background in
the combined Veto data of four quadrants, with a total of 7227 (+633,
-607) cts. The local mean background count rate was 1432 (+3, -5) cts/s.
We measure a T90 of 27 (+4, -2) s from the cumulative Veto light curve. 

CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC,
and PRL. The Indian Space Research Organisation funded, managed, and
facilitated the project.