////////////////////////////////////////////////////////////////////////
TITLE:   GCN CIRCULAR
NUMBER:  21540
SUBJECT: GRB 170817B: Fermi GBM detection
DATE:    17/08/18 04:12:29 GMT
FROM:    Oliver J Roberts at USRA/NASA  <oliver.roberts@nasa.gov>

O.J. Roberts (USRA) and C. Meegan (UAH) report on behalf of 
the Fermi GBM Team:

"At 21:47:34.43 UT on 17 August 2017, the Fermi Gamma-Ray 
Burst Monitor triggered and located GRB 170817B 
(trigger 524699259 / 170817908). The on-ground calculated 
location, using the GBM trigger data, is RA = 83.0, 
DEC = +50.1, with an uncertainty of 3.7 degrees (radius, 
1-sigma containment, statistical only; there is additionally 
a systematic error which we have characterized as a 
core-plus-tail model, with 90% of GRBs having a 3.7 deg error 
and a small tail suffering a larger than 10 deg systematic error. 
[Connaughton et al. 2015, ApJS, 216, 32] ).

The initial angle from the Fermi LAT boresight to
the GBM best location is 90 degrees.

The GBM triggered multiple short unresolvable pulses over a
total duration (T90) of 2.6 s (50-300 keV).
The time-averaged spectrum from T0+0.0 to T0+2.6 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.87 +/- 0.06 and
the cutoff energy, parameterized as Epeak, is 1120 +/- 228 keV

The event fluence (10-1000 keV) in this time interval is
(4.93 +/- 0.16)E-06 erg/cm^2. The 64 ms peak photon flux measured
starting from T0+0.0 s in the 10-1000 keV band
is 10.4 +/- 1.6 ph/s/cm^2.


The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

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TITLE:   GCN CIRCULAR
NUMBER:  21593
SUBJECT: GRB 170817B: Insight-HXMT observation
DATE:    17/08/19 13:32:35 GMT
FROM:    Shaolin Xiong at IHEP  <xiongsl@ihep.ac.cn>

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).

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 .