TITLE: GCN CIRCULAR NUMBER: 23038 SUBJECT: GRB 180724A: Insight-HXMT/HE detection DATE: 18/07/26 03:16:41 GMT FROM: Zhengwei Li at IHEP Y. Nang, C. K. Li., X. B. Li, J. Y. Liao, J. Guan, N. Sai, C. Wang, C. C. Guo, Y. Huang, G. Li, S. L. Xiong, C. Z. Liu, Z.W. Li, X. F. 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 2018-07-24T19:22:31.000 (T0), the Insight-HXMT/HE detected GRB 180724A in a routine search of the galactic plane survey data, which was also observed by Fermi/GBM (trigger number 554152956). The Insight-HXMT/HE light curve mainly consists of a bright pulse followed by a tail with a duration (T90) of 23.2 s measured from T0+1.6 s. The 1-second peak rate, measured from T0+3.7 s, is 1312.4 cnts/sec. The total counts from this burst is 15779.6 counts. URL_LC:http://www.hxmt.org/images/GRB/HEB180724807_CsI_lc.jpg. All measurements above are made with the CsI detectors operating in the low HV mode (previously called GRB mode) with the energy range of about 200-3000 keV (record energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and produce signals in the CsI detectors installed inside of the telescope. The NaI detectors also detected this pulse with a duration (T90) of 31.1 s from T0+1.6 s. The 1-second peak rate, measured from T0+7.8 s, is 239.3 cnts/sec. The total counts from this burst is 2859.7 counts. The energy range of NaI detectors are about 100-800 keV. URL_LC：http://www.hxmt.org/images/GRB/HEB180724807_NaI_lc.jpg 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.