  Gravitational perturbations in multi-planet systems caused by an accompanying
star are the subject of this investigation. Our dynamical model is based on the
binary star HD41004 AB where a giant planet orbits HD41004 A. We modify the
orbital parameters of this system and analyze the motion of a hypothetical
test-planet surrounding HD41004 A on an interior orbit to the detected giant
planet. Our numerical computations indicate perturbations due to mean motion
and secular resonances. The locations of these resonances are usually connected
to high eccentricity and highly inclined motion depending strongly on the
binary-planet architecture.As the positions of mean motion resonances can
easily be determined, the main purpose of this study is to present a new
semi-analytical method to determine the location of a secular resonance without
huge computational effort.
