TITLE: GCN CIRCULAR NUMBER: 23452 SUBJECT: GRB 181123B: Insight-HXMT/HE detection DATE: 18/11/26 06:54:25 GMT FROM: QiBin Yi at IHEP, HXMT Q. B. Yi, C. K. Li, X. B. Li, G. Li, J. Y. Liao, S. L. Xiong, C. Z. Liu, X. F. Li, Z. W. Li, Z. Chang, X. F. Lu, J. L. Zhao, A. M. Zhang, Y. F. Zhang, C. L. Zou (IHEP), Y. J. Jin, Z. Zhang (THU), T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, H. Y. Wang, M. Wu, Y. P. Xu, S. N. Zhang (IHEP), report on behalf of the Insight-HXMT team: At 2018-11-23T05:33:03.09 (T0), the Insight-HXMT/HE detected GRB 181123B (trigger ID: HEB181123231) in a routine search of the data, which was also detected by the SWIFT/BAT (J. P. Norris et al. 2018, GCN 23443) The Insight-HXMT/HE light curve mainly consists of a pulse with a duration (T90) of 0.23 s measured from T0+0.16 s. The 50-ms peak rate, measured from T0+0.28 s, is 5091.4 cnts/s. The total counts from this burst is 2060.5 counts. URL_LC: http://www.hxmt.org/images/GRB/HEB181123231_lc.jpg All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 80-800 keV (record energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was fundedjointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information could be found at: http://www.hxmt.org.