GRB 170805B

X. Ma, C. K. Li, Y. Huang, J. Y. Liao, S. L. Xiong, 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),
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 2017-08-05T14:18:49.70 (T0),
Insight-HXMT detected GRB 170805B (trigger ID: HEB170805596)
in a routine search of the data, which was also observed by
Konus-Wind (Kozlova et al., GCN 21442
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 ), INTEGRAL (SPI-ACS), and
Mars-Odyssey (HEND) (Hurley et al., GCN 21428
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 ).

The Insight-HXMT light curve mainly consists of a single pulse
with a duration (T90) of 0.035 s measured from T0+0.0005 s.
The 10-ms peak rate, measured from T0+0.02 s, is 6662.3 cnts/sec.
The total counts from this burst is 224 counts.

URL_LC: http://www.hxmt.org/images/GRB/HEB170805596_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 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 .

A.Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:

The short-duration GRB 170805B
(IPN triangulation: Hurley et al., GCN 21428
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 )
triggered Konus-Wind at T0=51527.165 s UT (14:18:47.165).

The burst light curve shows a single pulse
which starts at T0-32 ms and has a total duration of ~0.2 s.

As observed by Konus-Wind, the burst
had a fluence of 1.23(-0.21,+0.46)x10^-6 erg/cm2,
and a 16-ms peak flux, measured from T0-0.008 s,
of 2.25(-0.47,+0.89)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

Since the most intense part of the burst was detected before
the trigger, the spectral analysis was performed using
the KW 3-channel light curve data.

Modeling the KW 3-channel time-integrated spectrum
(from T0-0.032 s to T0+0.146 s)
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -0.97 (-0.15,+0.19), and Ep = 720 (-192,+474) keV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170805_T51527/

All the quoted errors are at the 68% confidence level.
All the quoted values are preliminary.

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,

D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team, and

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
report:

A short-duration GRB 170805B was detected by Konus-Wind,
INTEGRAL (SPI-ACS), and Mars-Odyssey (HEND)
at about 51525 s UT (14:18:45).

We have triangulated it to a preliminary, 3 sigma error box whose 
coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   137.274 (09h 09m 06s) +69.613 (+69d 36' 46")
  Corners:
   135.477 (09h 01m 54s) +69.580 (+69d 34' 49")
   136.562 (09h 06m 15s) +69.715 (+69d 42' 55")
   139.059 (09h 16m 14s) +69.622 (+69d 37' 18")
   137.975 (09h 11m 54s) +69.506 (+69d 30' 23")
  ---------------------------------------------
The error box area is 506 sq. arcmin, and its maximum
dimension is 1.25 deg (the minimum one is 9.6 arcmin).
The Sun distance was 52 deg.

This box may be improved.

Note that the positions of GRB 170805A and 170805B are inconsistent
with one another, ruling out a repeating source origin such as
a single magnetar.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB170805_T51527/IPN

The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.