[vsnet-grb-info 28005] GRB 210531A: AstroSat CZTI detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30108
SUBJECT: GRB 210531A: AstroSat CZTI detection
DATE:    21/06/01 06:59:20 GMT
FROM:    Gaurav Waratkar at IIT,Bombay  <gauravwaratkar at iitb.ac.in>

P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta
(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 long GRB 210531A, which
was also detected by AGILE/MCAL (GCN #30106) and Fermi (GCN #30105).

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
2021-05-31 12:00:04.5 UT. The measured peak count rate associated with
the burst is 1948 (+77, -87) cts/s above the background in the combined
data of four quadrants, with a total of 13005 (+281, -332) cts. The
local mean background count rate was 532 (+3.0, -2.9) cts/s. Using
cumulative rates, we measure a T90 of 20 (+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 2021-05-31 12:00:04.9 UT. The
measured peak count rate is 2541 (+104, -114) cts/s above the background
in the combined Veto data of four quadrants, with a total of 16360
(+452, -552) cts. The local mean background count rate was 1729 (+5, -5)
cts/s. We measure a T90 of 19 (+1, -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 [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