TITLE: GCN CIRCULAR NUMBER: 21921 SUBJECT: GRB 170906A: Insight-HXMT detection DATE: 17/09/24 03:22:42 GMT FROM: Yifei Zhang at IHEP Y. F. Zhang, S. L. Xiong, J. Y. Liao, C. K. Li, X. F. Lu, X. B. Li, C. Z. Liu, X. F. Li, Z. W. Li, Z. Chang, J. L. Zhao, A. M. 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 2017-09-06T00:43:06.00 (T0), Insight-HXMT/HE detected GRB 170906A (trigger ID: HEB170906029) in a routine search of the data,which is also detected by CALET (Penacchioni et al., GCN 21884), Fermi/GBM (Hamburg et al., GCN 21839) and Swift/BAT (Siegel et al., GCN 21821). The Insight-HXMT light curve mainly consists of multi-pulses with a duration (T90) of 64.6 s measured from T0+2.3 s. The 1-second peak rate, measured from T0+35.3 s, is 1870.6 cnts/sec. The total counts from this burst is 26305.3 counts. URL_LC: http://www.hxmt.org/images/GRB/HEB170906029_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 time-averaged spectrum from T0-5 s to T0+70 s is adequately fit by a Power Law model with spectral index = -2.70 +/- 0.06. The energy fluence is (5.94 +/- 0.20)E-04 erg/cm^2 in 200 - 5000 keV in this time interval. 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 .