[vsnet-grb-info 27263] GRB 210123A: AstroSat CZTI detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29366
SUBJECT: GRB 210123A: AstroSat CZTI detection
DATE:    21/01/29 05:46:19 GMT
FROM:    Gaurav Waratkar at IIT,Bombay  <gauravwaratkar at iitb.ac.in>

D. Nadella (NITK), G. Waratkar (IITB), A. Vibhute (IUCAA), S. Gupta 
(IUCAA), P. Sawant (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 210123A, which 
was also detected by Insight-HXMT/HE (GCN #29349) and Fermi-GBM (GCN 
#29351).

The source was detected in the 20-200 keV energy range. The light curve 
showed a single peak of emission at 2021-01-23 07:19:08.5 UT. Quadrant A 
was noisy, and we exclude it from further analysis. The measured peak 
count rate associated with the burst is 205 (+40, -38) cts/s above the 
background in the combined data of three quadrants (out of four), with a 
total of 996 (+259, -237) cts. The local mean background count rate was 
394 (+3, -3) cts/s. Using cumulative rates, we measure a T90 of 14 (+5, 
-4) 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 2021-01-23 07:19:09.1 UT in all 
four quadrants. The measured peak count rate is 1710 (+95, -102) cts/s 
above the background in the combined Veto data of four quadrants, with a 
total of 8982 (+648, -679) cts. The local mean background count rate was 
1817 (+5, -7) cts/s. We measure a T90 of 14 (+5, -1) 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.