//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30886 SUBJECT: GRB 210926A: GECAM detection DATE: 21/09/27 05:09:38 GMT FROM: Chao Zheng at IHEP C. Zheng, S. L. Xiong, X. Y. Zhao, Y. Huang, C. Cai, Z. W. Guo, C. Y. Li, S. Xiao, S. L. Xie, W. C. Xue, Q. B. Yi, Y. Zhao, Y. Q. Zhang, J. C. Liu, X. Y. Song, X. B. Li, P. Wang, J. Wang, Q. Luo, W. Chen, J. J. He, H. Wu, X. L. Zhang, C. W. Wang, P. Zhang, W. X. Peng, R. Qiao, D. Y. Guo, X. Ma, S. J. Zheng, G. Y. Zhao, Y. Q. Du, J. Liang, Z. Zhang, L. M. Song, F. J. Lu, S. N. Zhang (IHEP), report on behalf of GECAM team: During the commissioning phase, GECAM-B was triggered in-flight by a long burst, GRB 210926A, at 2021-09-26T20:52:28.250 UTC (denoted as T0). This burst consists of two episodes, with the first one triggered by Fermi/GBM (trigger ID: 654382283). Both episodes were triggered by GECAM-B with the on-ground pipeline. Its alert data was promptly downlinked to the ground through the short message service of BeiDou Navigation Satellite System (BDS). The time latency of the first BeiDou message relative to the trigger time is about 1 minute. According to the BDS alert data, this burst mainly consists of multiple pulses with duration of about 90 s. The GECAM light curve could be found here: http://twiki.ihep.ac.cn/pub/GECAM/GRBList/GRB_210926A.png GECAM-B localized this burst to the following position (J2000): Ra: 351.51 deg Dec: -18.21 deg Err: 2.86 deg (1-sigma, statistical only) The current systematic error of location is estimated to be several degrees which could be minimized by the ongoing calibration. The GECAM preliminary location could be found here: http://twiki.ihep.ac.cn/pub/GECAM/GRBList/210926Aloc.png This location is consistent with Fermi/GBM position within the error. Please note that all GECAM results here are preliminary. The final analysis will be published in journal papers or GECAM online catalog. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time), which was funded by the Chinese Academy of Sciences (CAS). //////////////////////////////////////////////////////////////////////// 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 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.