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GCN Circular 31521

Subject
GRB 220124A: AstroSat CZTI detection of a bright long GRB
Date
2022-01-24T08:11:18Z (2 years ago)
From
Gaurav Waratkar at IIT,Bombay <gauravwaratkar@iitb.ac.in>
V. Prasad (IUCAA), G. Waratkar (IITB), A. Suresh (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 the CIFT framework (Sharma et al., 2021,
JApA, 42, 73) showed detection of a long GRB 220124A.

The source, consisting of three distinct bursts, was clearly detected in
the 20-200 keV energy range. The strongest peak is at 2022-01-24
03:39:19.00 UT. The measured peak count rate associated with the burst
is 441 (+16, -17) cts/s above the background in the combined data of
four quadrants, with a total of 25670 (+1334, -1297) cts. The local mean
background count rate was 496 (+1, -1) cts/s. Using cumulative rates, we
measure a T90 of 231 (+4, -5) s.

All three bursts from the source were also clearly detected in the CsI
anticoincidence (Veto) detector in the 100-500 keV energy range. The
strongest peak is at 2022-01-24 03:39:24.32 UT. The measured peak count
rate is 6829 (+76, -81) cts/s above the background in the combined Veto
data of four quadrants, with a total of 362309 (+6293, -4918) cts. The
local mean background count rate was 16030 (+5, -11) cts/s. We measure a
T90 of 231 (+38, -2) s from the cumulative Veto light curve. 

We note that the burst has not been localised, and we cannot rule out an
association with any SGRs. The ASIMOV tool
(http://astrosat-ssc.iucaa.in:8080/ASIMOV/ASIMOV [1]) indicates that
other active missions were covering different parts of the sky, hence
confirmed non-detections from other missions can help localise the
source by inferring earth-occulted regions.

CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb [2]. 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. 

Links:
------
[1] http://astrosat-ssc.iucaa.in:8080/ASIMOV/ASIMOV
[2] http://astrosat.iucaa.in/czti/?q=grb
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