GCN Circular 21593

Z. W. Li, J. Y. Liao, C. K. Li, X. B. Li, S. L. Xiong, C. Z. Liu,
X. F. Li, Z. Chang, X. F. Lu, J. L. Zhao, A. M. Zhang, Y. F. Zhang,
C. L. Zou (IHEP), Y. J. Jin, X. Ma, 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 2017-08-17T21:47:34.00 (T0),
Insight-HXMT detected GRB 170817B (trigger ID: HEB170817908)
in a routine search of the data, which was also observed by
Fermi/GBM (Roberts et al. 2017, GCN 21540
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 ).

The Insight-HXMT light curve consists of multiple pulses
with a duration (T90) of 2.64 s measured from T0+0.40 s.
The 50-ms peak rate, measured from T0+0.40 s, is 6135.4 cnts/sec.
The total counts from this burst is 5353.1 counts.

URL_LC: http://www.hxmt.org/images/GRB/HEB170817908_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 to T0+3.60 s is
adequately fit by a Power Law model with spectral index = -1.60 +/- 0.05.
The energy fluence is (1.09 +/- 0.05)E-05 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 .