TITLE: GCN CIRCULAR NUMBER: 22171 SUBJECT: GRB 171124A: Insight-HXMT/HE detection DATE: 17/11/27 14:06:03 GMT FROM: Li Xufang at IHEP X.F. Li, S. L. Xiong, X. B. Li, C. K. Li, C. Z. Liu, 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: During the commissioning phase, at 2017-11-24T05:38:03.000 (T0), Insight-HXMT/HE detected GRB 171124A (trigger ID: HEB171124234) in a routine search of the data, which was also observed by Fermi-LAT (F. Longo et al, GCN Circ.22156), Fermi/GBM(E. Bissaldi et al, GCN Circ.22164),AstroSat CZTI(V. Sharma et al,GCN Circ.22168). The Insight-HXMT light curve mainly consists of two emission episodes with a duration (T90) of 17.27 s measured from T0-5.66 s. The 1-s peak rate, measured from T0-0.007 s, is 924.7 cnts/sec. The total counts from this burst is 3968.2 counts. URL_LC: http://www.hxmt.org/images/GRB/HEB171124234_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. The analysis results presented above are preliminary; final results will be published elsewhere. 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/index.php/enhome .