GRB 170207A

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

K. Hurley, on behalf of the IPN,

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

S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer,
on behalf of the Swift-BAT team, report:

The long-duration, very bright GRB 170207A has been
detected by Fermi (GBM trigger 508196708), Konus-Wind, INTEGRAL 
(SPI-ACS), and Swift (BAT), so far, at about 78304 s UT (21:45:04).
The burst was outside the coded field of view of the BAT.

We have triangulated it to a preliminary, 3 sigma error box whose
coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   315.704 (21h 02m 49s) +55.690 (+55d 41' 25")
  Corners:
   307.259 (20h 29m 02s) +52.583 (+52d 35' 00")
   325.165 (21h 40m 40s) +58.232 (+58d 13' 54")
   324.653 (21h 38m 37s) +57.713 (+57d 42' 46")
   306.905 (20h 27m 37s) +51.893 (+51d 53' 34")
  ---------------------------------------------
The error box area is 4.66 sq. deg, and its maximum
dimension is 12.17 deg (the minimum one is 24.0 arcmin).
The Sun distance was 70 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB170207_T78301/IPN/

The time history and spectrum will be given in forthcoming GCN Circulars.

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 long-duration, very bright GRB 170207A
(IPN triangulation: Svinkin et al, GCN Circ. 20628
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 )
triggered Konus-Wind at T0=78301.73 s UT (21:45:01.730).

The burst light curve shows three multipeaked emission episodes
which started at ~T0-0.3 s and had a total duration of ~42 s.
The emission is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170207_T78301/

As observed by Konus-Wind, the burst
had a fluence of 7.84(-0.96,+0.85)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+18.016 s,
of 1.50(-0.21,+0.26)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+41.984 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 = -0.86(-0.06,+0.06),
the high energy photon index beta = -2.63(-0.84,+0.26),
the peak energy Ep = 394(-33,+42) keV
(chi2 = 106/97 dof)

The spectrum near the maximum count rate
(measured from T0+13.824 to T0+18.944 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 = -0.63(-0.08,+0.08),
the high energy photon index beta = -3.60(-6.40,+0.83),
the peak energy Ep = 524(-46,+56) keV
(chi2 = 107/82 dof)

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

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

"At 21:45:03.67 UT on February 7th 2017, the Fermi Gamma-Ray
Burst Monitor triggered and located GRB 170207A
(trigger 508196708 /170207906). This event was also detected 
by Konus Wind (Svinkin et al, GCN 20629
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 ) and localized by the 
IPN (Svinkin et al, GCN 20628
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 ). The on-ground calculated location 
using the GBM trigger data is,

RA = 325.87, DEC = +50.05 (J2000 degrees), equivalent to
J2000 21h 43m, +50d 03',

with an uncertainty of 1 degree (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
ground-location is 94 degrees.

The GBM light curve shows a long burst with multiple
episodes of bright emission over a duration (T90) of about 
39 s (50-300 keV). The time-averaged spectrum from T0+0 s to 
T0+39 s is best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -0.92 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 499.4 +/- 19.5 keV.

A Band function fits the spectrum equally well, with
alpha= -0.91 +/- 0.02, beta= -2.68 +/- 0.28 and Epeak
is 478.8 +/- 23.1 keV.

The event fluence (10-1000 keV) in this time interval is
(5.86 +/- 0.07) E-05 erg/cm^2. The 1s peak photon flux
measured starting from T0+20.5 s in the 10-1000 keV band is
25.4 +/- 0.4 ph/s/cm^2.

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

V. Sharma and D. Bhattacharya (IUCAA), V. Bhalerao (IITB), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:

Analysis of AstroSat CZTI data showed a clear detection of GRB170207A (IPN Triangulation detection: D. Svinkin et al., GCN Circ. 20628
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 ) in the 40-200 keV energy range. The light curve shows multiple peaks. The first peak occurred at 21:45:08.67 UT, 5 s after the Fermi trigger (Fermi GBM detection: O.J. Roberts., GCN circular 20630
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 ) and a second group of peaks was detected 18 s after the trigger. An interval of ~ 5 s between these two showed no detectable emission. The measured peak count rate is 345 counts/s above the background in combined data of four quadrants, with a total 2332.5 counts. The local mean background count rate was 352 counts/s. Using cumulative rates, we measure a T90 of 36.5 s.

It was clearly detected in the CsI anticoincidence detector (Veto) also as bright detection in the 100-500 keV energy range.

CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.

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


At 2017-02-07T21:45:04.00 UT (T0), during a routine on-ground 
search of data, POLAR detected the GRB 170207A, 
which was also detected by the 
Fermi/GBM (trigger 508196708/170207906, O.J. Roberts et al,
Circ 20630), IPN Triangulation(D. Svinkin et al, Circ 20628)
and Konus-Wind (D. Svinkin et al, Circ 20629).


The POLAR light curve consists of multiple peaks,
with a duration (T90) of 39.47 s measured from T0+0.82 s.
The 1-s peak rate measured from T0+17.00 s is 6318.2 cnts/s.
The total counts is about 63182 cnts. The above measurements
are in the energy range of about 20-500 keV.


LC_URL:
http://polar.ihep.ac.cn/grb/2017/02/GRB170207A/lc/POLAR_lc_grb170207A.png


Using the best location from the IPN Triangulation, which is (J2000):
RA:     315.704   [deg]
Dec:    +55.690   [deg]
Err:    4.66      [sq. deg]


the incident angle in POLAR coordinate at T0 is:
theta:  70.6      [deg]
phi:    -2.2      [deg]


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/.