TITLE: GCN CIRCULAR NUMBER: 21457 SUBJECT: LIGO/Virgo G296853: Insight-HXMT observations DATE: 17/08/11 14:41:44 GMT FROM: Shaolin Xiong at IHEP J. Y. Liao, X. B. Li, C. K. Li, M. Y. Ge, Y. Huang, S. L. Xiong, Y. Liu, 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: Insight-HXMT was taking data normally around the LIGO trigger time (T0=2017-08-09 08:28:21.747 UTC). At T0, more than 95% of the LIGO localization region was covered by the Insight-HXMT without occultation by the Earth. Within T0 +/- 1000 s, no significant events (SNR > 5 sigma) are found in a search of the Insight-HXMT raw light curves with time scales of 20 ms, 50 ms, 0.2 s and 1 s, respectively. Only one particle event lasting about 180 s was found at T0-680 s, which is caused by the orbital environment thus has no relation with the LIGO event. With the three typical GRB Band spectral models, three integration time (1 s, 10 s, and 100 s) and the LIGO localization region, the 3-sigma upper-limits fluence (0.2 - 5 MeV, incident energy) are reported below: Band model 1 (alpha=-1.9, beta=-3.7, Ep=70 keV): 1s: 1.4e-07 to 2.6e-07 erg cm^-2 10s: 4.5e-07 to 9.1e-07 erg cm^-2 100s: 1.6e-06 to 3.1e-06 erg cm^-2 Band model 2 (alpha=-1.0, beta=-2.3, Ep=230 keV): 1s: 2.2e-07 to 3.9e-07 erg cm^-2 10s: 7.2e-07 to 1.4e-06 erg cm^-2 100s: 2.5e-06 to 4.6e-06 erg cm^-2 Band model 3 (alpha=-0.0, beta=-1.5, Ep=1000 keV): 1s: 5.2e-07 to 7.5e-07 erg cm^-2 10s: 1.6e-06 to 2.5e-06 erg cm^-2 100s: 5.8e-06 to 8.4e-06 erg cm^-2 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; refined results will be reported later. 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 .