TITLE:   GCN CIRCULAR
NUMBER:  30889
SUBJECT: GRB 210926A: AstroSat CZTI detection
DATE:    21/09/27 13:36:09 GMT
FROM:    Gaurav Waratkar at IIT,Bombay  <gauravwaratkar@iitb.ac.in>

P. Sawant (IUCAA), G. Waratkar (IITB), V. Prasad (IUCAA), 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.,
2021, JApA, 42, 73) showed detection of a long GRB 210926A, which was
also detected by GECAM (C. Zheng et al., GCN 30886).

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
2021-09-26 20:52:27.5 UT. The measured peak count rate associated with
the burst is 250 (+51, -16) cts/s above the background in the combined
data of four quadrants, with a total of 3971 (+446, -463) cts. The local
mean background count rate was 480 (+3, -3) cts/s. Using cumulative
rates, we measure a T90 of 26 (+6, -5) 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 2021-09-26 20:52:30.9 UT. The
measured peak count rate is 262 (+73, -38) cts/s above the background in
the combined Veto data of four quadrants, with a total of 3091 (+703,
-866 cts. The local mean background count rate was 1512 (+5, -4) cts/s.
We measure a T90 of 25 (+14, -10) 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.