TITLE: GCN CIRCULAR NUMBER: 27679 SUBJECT: Insight-HXMT X-ray and hard X-ray upper limits to the radio burst detected by FAST from SGR 1935+2154 DATE: 20/05/03 12:09:44 GMT FROM: Shaolin Xiong at IHEP C. K. Li, Y. L. Tuo, M. Y. Ge, X. B. Li, J. Y. Liao, C. Cai, S. L. Xiong, C. Z. Liu, Y. Chen, X. L. Cao (IHEP), T. P. Li (IHEP/THU), S. M. Jia, J. Y. Nie, F. J. Lu, L. M. Song, M. Wu, Y. P. Xu, S. N. Zhang (IHEP), L. Lin (BNU), B. Zhang (UNLV), report on behalf of the Insight-HXMT team: Around the trigger time (T0=2020-04-30T21:43:00.5 UTC) of the highly polarised radio burst event reported by FAST (ATel #13699), Insight-HXMT was carrying out the ToO observation of SGR 1935+2154 without any occultation by the Earth. Within T0 +/- 50 s, no significant excess events (SNR > 3 sigma) are found in a search of the Insight-HXMT LE (1-10 keV), ME(10-30 keV) and HE (27-250 keV) light curves. Assuming the same spectral model to the X-ray counterpart that we reported in ATel #13687, and with one second timescale (1 s) coming from the position of SGR1935+2154, the 3-sigma fluence upper-limits are as following: Model: wabs*Cutoffpl (nH=2.6,PhoIndex=1.44, Ecut=69.8 keV): LE:  2.68e-09 erg cm^-2 ME:  3.45e-09 erg cm^-2 HE:  4.46e-09 erg cm^-2 Insight-HXMT will continue to observe SGR 1935+2154 with LE, ME and HE until 2020-05-06 01:20:47 UT. 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 could be found at: http://www.hxmt.org.