[vsnet-grb-info 28590] GRB 210822A: AstroSat CZTI detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30693
SUBJECT: GRB 210822A: AstroSat CZTI detection
DATE:    21/08/23 09:13:47 GMT
FROM:    Gaurav Waratkar at IIT,Bombay  <gauravwaratkar at iitb.ac.in>

V. Prasad (IUCAA), P. Sawant (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 CIFT framework (Sharma et al,
2020, arxiv:2011.07067) showed detection of a bright long GRB 210822A,
which was also detected by Swift (Page et al., GCN 30677), GECAM (Wang
et al., GCN 30678), and Fermi-LAT (Ohno et al., GCN 30687). 

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
2021-08-22 09:18:17.50 UT. The measured peak count rate associated with
the burst is 2190 (+85, -91) cts/s above the background in the combined
data of four quadrants, with a total of 12961 (+301, -314) cts. The
local mean background count rate was 530 (+2, -3) cts/s. Using
cumulative rates, we measure a T90 of 10 (+0.2, -0.2) 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 2021-08-22 09:18:18.97 UT. The
measured peak count rate is 3587 (+117, -127) cts/s above the background
in the combined Veto data of four quadrants, with a total of 24196
(+541, -655) cts. The local mean background count rate was 1799 (+4, -4)
cts/s. We measure a T90 of 12 (+0.5, -0.5) 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 [1]. 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:
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[1] http://astrosat.iucaa.in/czti/?q=grb