GCN Circular 21307

S. L. Xiong, C. K. Li, J. Y. Liao, 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), M. Gao (IHEP), T. P. Li (IHEP/THU), M. S. Li,
H. W. Liu, F. J. Lu, L. M. Song, W. H. Tao, H. Y. Wang, X. Y. Wen, M. Wu,
H. Xu, Y. P. Xu, C. M. Zhang, F. Zhang, J. Zhang, T. Zhang,
S. N. Zhang (IHEP), report on behalf of the Insight-HXMT team:

During the commissioning phase, at 2017-07-08T01:06:11.25 (T0),
Insight-HXMT detected GRB 170708A (trigger ID: HEB170708045)
in a routine search of the data, which was also observed by the Fermi/GBM
(Trig# 521168776) and SPI-ACS (Trig time 2017-07-08T01:06:10.708).

The Insight-HXMT light curve consists of a single pulse
with a duration (T90) of 0.22 s measured from T0-0.05 s.
The 50-ms peak rate, measured from T0+0 s, is 3553.6 cnts/sec.
The total counts from this burst is 369 counts.

All measurements above are made with the CsI detectors operating in the
GRB mode, in which the energy range is increased to about 200 - 3000 keV
(record energy) , compared to the normal mode of 80 - 800 keV.
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.

URL_LC: http://www.hxmt.org/images/GRB/HEB170708045_lc.jpg

This is a weak short burst. The detection significance of Insight-HXMT
is ~10 sigma. The burst emission is seen up to ~1 MeV.

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 .