TITLE: GCN CIRCULAR NUMBER: 21444 SUBJECT: GRB 170805B: Insight-HXMT observation DATE: 17/08/10 12:16:32 GMT FROM: Shaolin Xiong at IHEP X. Ma, C. K. Li, Y. Huang, 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: During the commissioning phase, at 2017-08-05T14:18:49.70 (T0), Insight-HXMT detected GRB 170805B (trigger ID: HEB170805596) in a routine search of the data, which was also observed by Konus-Wind (Kozlova et al., GCN 21442), INTEGRAL (SPI-ACS), and Mars-Odyssey (HEND) (Hurley et al., GCN 21428). The Insight-HXMT light curve mainly consists of a single pulse with a duration (T90) of 0.035 s measured from T0+0.0005 s. The 10-ms peak rate, measured from T0+0.02 s, is 6662.3 cnts/sec. The total counts from this burst is 224 counts. URL_LC: http://www.hxmt.org/images/GRB/HEB170805596_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 .