TITLE:   GCN CIRCULAR
NUMBER:  30892
SUBJECT: GRB 210925B: AstroSat CZTI detection
DATE:    21/09/28 13:24:23 GMT
FROM:    Gaurav Waratkar at IIT,Bombay  <gauravwaratkar@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.,
2021, JApA, 42, 73) showed detection of a long GRB 210925B for which the
IPN triangulation (Hurley et al., GCN 30890) was reported. 

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
2021-09-25 01:20:09.75 UT. The measured peak count rate associated with
the burst is 887 (+190, -97) cts/s above the background in the combined
data of four quadrants, with a total of 1482 (+214, -230) cts. The local
mean background count rate was 471 (+5, -9) cts/s. Using cumulative
rates, we measure a T90 of 6.3 (+1.9, -2.0) s. 

It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range. 

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.