We have investigated the formation of a circumstellar wide-orbit gas giant planet in a multiple stellar system .
We consider a model of orbital circularization for the core of a giant planet after it is scattered from an inner disk region by a more massive planet , which was proposed by \citet khi14 .
We extend their model for single star systems to binary ( multiple ) star systems , by taking into account tidal truncation of the protoplanetary gas disk by a binary companion .
As an example , we consider wide-orbit gas giant in a hierarchical triple system , HD131399Ab .
The best-fit orbit of the planet is that with semimajor axis \sim 80 au and eccentricity \sim 0.35 .
As the binary separation is \sim 350 au , it is very close to the stability limit , which is puzzling .
With the original core location \sim 20 -30 au , the core ( planet ) mass \sim 50 M _ { E } and the disk truncation radius \sim 150 au , our model reproduces the best-fit orbit of HD131399Ab .
We find that the orbit after the circularization is usually close to the stability limit against the perturbations from the binary companion , because the scattered core accretes gas from the truncated disk .
Our conclusion can also be applied to wider or more compact binary systems if the separation is not too large and another planet with \ga 20-30 Earth masses that scattered the core existed in inner region of the system .