GRB 170206A

A. von Kienlin (MPE) and O.J. Roberts (USRA/NASA-MSFC) report 
on behalf of the Fermi GBM Team:

"At 10:51:57.70 UT on February 6th 2017, the Fermi Gamma-Ray
Burst Monitor triggered and located GRB 170206A
(trigger 508071122 /170206453). The on-ground calculated 
location, using the GBM trigger data, 

is RA = 211.80, DEC = +13.06, (J2000 degrees, equivalent to 
J2000 14h 07m, +/- 13d 03')

with an uncertainty of 1.14 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 trigger resulted in an Autonomous Repoint Request (ARR) 
by the GBM Flight Software owing to the high peak flux of the 
GRB. This ARR was accepted and the spacecraft slewed to the 
GBM in-flight location. The initial angle from the Fermi-LAT 
boresight to the GBM ground location is 67 degrees.

The GBM light curve shows a short, bright burst with a duration 
(T90) of about 1.2 s (50-300 keV). The time-averaged spectrum 
from T0+0.1s to T0+1.3 s is best fit by a BAND function, with 
alpha=  -0.28 +/- 0.04, beta= -2.55 +/- 0.12 and Epeak, 
is 341 +/- 13 keV.

The event fluence (10-1000 keV) in this time interval is
(1.34 +/- 0.02) E-05 erg/cm^2. The 64 ms peak photon flux 
measured starting from T0+0.6 s in the 10-1000 keV band is
57.0 +/- 2.1 ph/s/cm^2.

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

GRB 170206A: Fermi-LAT detection

F. Fana Dirirsa (U. Johannesburg ), D.Tak (UMD/NASA-GSFC), G. Vianello (Stanford Univ.), J. Racusin (NASA/GSFC), D. Kocevski (NASA/MSFC)  report on behalf of the Fermi-LAT team:

At 10:51:57.70 on February, 06, 2017 Fermi-LAT detected high-energy emission from GRB 170206A which was also detected by Fermi-GBM starting at 10:51:57.70 UT (trigger 508071122 /170206453; Oliver J Roberts et al. GCN 20616
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 ).  

The best LAT on-ground location is found to be

RA, Dec = 212.79,  14.48 (J2000)

with an error radius of 0.85 deg (90 % containment, statistical error only). 

This was 67 deg from the LAT boresight at the time of the trigger.

The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the trigger with high significance. 

The highest-energy photon is a 811 MeV event which is observed 5.17 seconds after the GBM trigger.

The Fermi-LAT point of contact for this burst is Feraol Fana Dirirsa (fdirirsa@uj.ac.za <mailto:fdirirsa@uj.ac.za> ).

The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.

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,

V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa,
and A. Goldstein, on behalf of the Fermi GBM team,

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

and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

The short-duration, hard-spectrum GRB 170206A
(Fermi-GBM detection: von Kienlin and Roberts, GCN Circ. 20616
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 ;
Fermi-LAT detection: Fana Dirirsa et al., GCN Circ. 20617
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 )
was detected by Fermi (GBM), Konus-Wind, INTEGRAL (SPI-ACS),
and Mars-Odyssey (HEND) at about 39118 s UT (10:51:58).

We have triangulated it to a preliminary, 3 sigma error box whose
coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   212.633 (14h 10m 32s) +14.238 (+14d 14' 17")
  Corners:
   212.341 (14h 09m 22s) +14.997 (+14d 59' 50")
   212.901 (14h 11m 36s) +14.095 (+14d 05' 41")
   212.915 (14h 11m 40s) +13.455 (+13d 27' 20")
   212.365 (14h 09m 28s) +14.378 (+14d 22' 41")
  ---------------------------------------------
The error box area is 1156 sq. arcmin, and its maximum
dimension is 1.64 deg (the minimum one is 18.2 arcmin).
The Sun distance was 110 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB170206_T39121/IPN/

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

Yuanhao Wang (IHEP), Shaolin Xiong (IHEP), Yi Zhao (IHEP)
report on behalf of the POLAR collaboration:

At 2017-02-06T10:51:57.70 UT (T0), during a routine on-ground 
search of data, POLAR detected the GRB 170206A, which was 
also detected by Fermi/GBM
(trigger 508071122/170206453; A. von Kienlin et al. GCN 20616
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 ), 
Fermi/LAT(F. Fana Dirirsa et al. GCN 20617
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 ) and 
INTEGRAL/SPIACS(trigger_num 7680).

The POLAR light curve consists of multiple peaks,
with a duration (T90) of 1.194 s measured from T0+0.147 s.
The 0.1s peak rate measured from T0+0.4s is 16145.2 cnts/s.
The total counts is about 12918 cnts.
LC_URL:
http://polar.ihep.ac.cn/grb/2017/02/GRB170206A/lc/POLAR_lc_grb170206A.png

The above result is not dead time corrected. The above 
measurements are in the energy range of about 20-500 keV.

Using the best location from the Fermi/LAT, which is (J2000):
RA:   212.79��[deg]
Dec:  +14.48��[deg]
Err:  0.85����[deg] (90% containment, statistical error only)

the incident angle in POLAR coordinate at T0 is:
theta: 19.5   [deg]
phi:   148.70 [deg]

The Minimum Detectable Polarization(MDP) for this burst is
estimated to be ~5.7% [1-sigma, statistical only]. 
Follow-up observations are strongly encouraged.

All analysis results presented above are preliminary.

POLAR is a dedicated Gamma-Ray Burst polarimeter (50-500 keV)
on-board the Chinese space laboratory Tiangong-2 launched on
Sep 15,2016. More information about POLAR can be found at 
http://polar.ihep.ac.cn/en/ , http://isdc.unige.ch/polar/
and http://polar.psi.ch/pub/ .

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

The short-duration, hard-spectrum, bright GRB 170206A
(Fermi-GBM detection: von Kienlin and Roberts, GCN Circ. 20616
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 ;
Fermi-LAT detection: Fana Dirirsa et al., GCN Circ. 20617
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 ;
IPN triangulation: Hurley et al., GCN Circ. 20623
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 )
triggered Konus-Wind at T0=39121.226 s UT (10:52:01.226).

The burst light curve shows a multipeaked structure
started at ~T0-0.2 s with a total duration of ~1.5 s.
The emission is seen up to ~15 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170206_T39121/

As observed by Konus-Wind, the burst
had a fluence of 1.49(-0.15,+0.16)x10^-5 erg/cm2,
and a 16-ms peak flux, measured from T0+0.306 s,
of 3.30(-0.64,+0.66)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+1.280 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = 0.00(-0.20,+0.24),
the high energy photon index beta = -2.28(-0.18,+0.13),
the peak energy Ep = 260(-29,+33) keV
(chi2 = 58/61 dof)

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.