TITLE: GCN CIRCULAR NUMBER: 29349 SUBJECT: GRB 210123A: Insight-HXMT/HE detection DATE: 21/01/24 05:44:27 GMT FROM: Wangchen Xue at IHEP W. C. Xue, C. Cai, J. C. Liu, Q. Luo, S. Xiao, Q. B. Yi, Y. Q. Zhang, C. Zheng, Y. Huang, C. K. Li, G. Li, X. B. Li, J. Y. Liao, X. Y. Song, S. L. Xiong, C. Z. Liu, X. F. Li, Z. W. Li, Z. Chang, A. M. Zhang, Y. F. Zhang, X. F. Lu, C. L. Zou (IHEP), Y. J. Jin, Z. Zhang (THU), T. P. Li (IHEP/THU), F. J. Lu, L. M. Song, M. Wu, Y. P. Xu, S. N. Zhang (IHEP), report on behalf of the Insight-HXMT team: At 2021-01-23T07:19:10.350 (T0), Insight-HXMT/HE detected GRB 210123A (trigger ID: HEB210123304) in a routine search of the data, which also triggered INTEGRAL and IPN. The Insight-HXMT/HE light curve mainly consists of multiple pulses with a duration (T90) of 6.56 s measured from T0-0.52 s. The 1-ms peak rate, measured from T0+1.95 s, is 1825 cnts/sec. The total counts from this burst is 5536 counts. URL_LC: http://twiki.ihep.ac.cn/pub/HXMT/GRBList/HEB210123304_lc.jpg All measurements above are made with the CsI detectors operating in the GRB mode with the energy range of about 80-800 keV (deposited 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 funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org.