Stability of habitable Trojan planets at HD 23079

Case Studies of Habitable Trojan Planets in the System of HD 23079

Investigations of whether Trojan planets could be stable in the habitable zone of the HD 23079 system. In one case the Trojan planet was captured as a retrograde satellite of the gas giant. Whether Trojan planets could actually form in this system is not dealt with.

Unless I missed it, they don't seem to describe how this planet would be captured by gas giant.

Prograde and retrograde habitable moons are possible, too.
http://arxiv.org/abs/1304.1157