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GCN Circular 31367

Subject
GRB 211231A: AstroSat CZTI detection
Date
2022-01-02T12:16:26Z (2 years ago)
From
Gaurav Waratkar at IIT,Bombay <gauravwaratkar@iitb.ac.in>
V. Prasad (IUCAA), A. Suresh (IITB), 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 CIFT framework (Sharma et al.,
2021, JApA, 42, 73) showed detection of a long GRB 211231A which was
also detected by Fermi-GBM (GCN 31343) and GECAM (Guo et al. GCN 31345).
 

The source was clearly detected in the 20-200 keV energy range. The
light curve peaks at 2021-12-31 07:00:35.75 UT. The measured peak count
rate associated with the burst is 193 (+60, -27) cts/s above the
background in the combined data of three quadrants, with a total of 599
(+188, -196) cts. The local mean background count rate was 362 (+4, -4)
cts/s. Using cumulative rates, we measure a T90 of 13 (+1, -7) s. 

It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range. The light curve peaks at 2021-12-31
07:00:35.88 UT. The measured peak count rate is 562 (+73, -75) cts/s
above the background in the combined Veto data of four quadrants, with a
total of 1536 (+452, -569) cts. The local mean background count rate was
1590 (+4, -4) cts/s. We measure a T90 of 8 (+3, -6) 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.
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