TITLE: GCN CIRCULAR NUMBER: 30549 SUBJECT: GRB 210727A: AstroSat CZTI detection DATE: 21/07/30 06:21:59 GMT FROM: Gaurav Waratkar at IIT,Bombay 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 short GRB 210727A, which was also detected by Fermi-GBM (Trigger no. 649072251), AGILE/MCAL (Ursi et al., GCN 30533), CALET (Akaike et al., GCN 30544), with IPN localization (Ridnaia et al., GCN 30541) and BALROG localization (Biltzinger et al., GCN 30531). 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 2021-07-27 09:50:46.45 UT. The measured peak count rate associated with the burst is 890 (+197, -153) cts/s above the background in the combined data of four quadrants, with a total of 489 (+74, -67) cts. The local mean background count rate was 482 (+11, -15) cts/s. Using cumulative rates, we measure a T90 of 0.9 (+0.3, -0.1) s. It was also 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.