TITLE: GCN CIRCULAR NUMBER: 22116 SUBJECT: GRB 171103A: Insight-HXMT observation DATE: 17/11/10 07:57:17 GMT FROM: Shaolin Xiong at IHEP G. Li, J. Y. Liao, S. L. Xiong, C. K. Li, X. B. Li, C. Z. Liu, X. F. Li, Z. W. Li, X. F. Lu, 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 2017-11-03T23:10:32.04 (T0), Insight-HXMT/HE detected GRB 171103A (trigger ID: HEB171103965) in a routine search of the data,which is also detected by Swift/BAT (Ukwatta et al.,GCN 22095), Fermi/GBM (Veres et al., GCN 22100), Konus-Wind (Tsvetkova et al.,GCN 22101) and AstroSat/CZTI (Sharma et al., GCN 22103). The Insight-HXMT light curve mainly consists of multi-pulses with a duration (T90) of 0.21 s measured from T0+0.033 s. The 10-ms peak rate, measured from T0+0.096 s, is 19946.0 cnts/sec. The total counts from this burst is 2915.7 counts. URL_LC: http://www.hxmt.org/images/GRB/HEB171103965_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+0.05 s to T0+0.30 s is adequately fit by a Power Law model with spectral index = -0.97 ± 0.07. The energy fluence is (4.1 ± 0.3)e-6 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 could be found at: http://www.hxmt.org/index.php/enhome .