TITLE: GCN CIRCULAR NUMBER: 23275 SUBJECT: GRB 180925A: Insight-HXMT/HE detection DATE: 18/09/27 06:44:05 GMT FROM: Qi Luo at IHEP Q. Luo,Y. Huang,G. Li,S. L. Xiong,X. B. Li, C. K. Li, C.Z. Liu, X.F. Li, Z. W. Li, Z. Chang, J. L. Zhao, 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, H. Y. Wang, M. Wu, Y. P. Xu, S. N. Zhang (IHEP), report on behalf of the Insight-HXMT team: At 2018-09-25T14:37:27.900 (T0), the Insight-HXMT/HE detected GRB 180925A(trigger ID: HEB180925609) in a routine search of the data, which was also triggered by Swift-BAT (Gropp et al.,GCN 23268). The Insight-HXMT/HE light curve mainly consists of a bright pulse with a duration (T90) of 23.23 s measured from T0-2.82 s. The 1-s peak rate, measured from T0+1.8640 s, is 1845.76 cnts/sec. The total counts from this burst is 10107.89 counts. URL_LC: http://www.hxmt.org/images/GRB/HEB180925609_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 fundedjointly 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.