[vsnet-grb-info 28284] GRB 210704B: AstroSat CZTI detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  30387
SUBJECT: GRB 210704B: AstroSat CZTI detection
DATE:    21/07/06 04:14:59 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 long GRB 210704B, which
was also detected by Fermi - GBM (Malacaria et al. 2021, GCN 30382). 

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
2021-07-04 16:25:47.5 UT. The measured peak count rate associated with
the burst is 296 (+47, -39) cts/s above the background in the combined
data of four quadrants, with a total of 3398 (+476, -466) cts. The local
mean background count rate was 552 (+2, -3) cts/s. Using cumulative
rates, we measure a T90 of 37 (+8, -7) s. 

It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range. The Veto light curve showed multiple
peaks of emission with the strongest peak at 2021-07-04 16:25:46.7 UT.
The measured peak count rate is 1642 (+95, -104) cts/s above the
background in the combined Veto data of four quadrants, with a total of
18239 (+789, -1081) cts. The local mean background count rate was 1864
(+5, -5) cts/s. We measure a T90 of 34 (+9, -3) 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.