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
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 ) 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 . 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.