Dynamics of passing-stars-perturbed binary star systems

We investigate the dynamical effects of a sequence of close encounters between a binary star system and passing stars within 100 Myr. We focus on two Sun-like stars with various orbital separations $a_{\scriptscriptstyle 0}$ initially on circular-planar orbits. We treat the problem statistically since the mass of the perturber varies from 0.1$M_{\odot}$ to 10$M_{\odot}$ and close encounter distances between 500 -- 5000 au. In addition, each sequence is cloned 100 times. We show that binaries with $a_{\scriptscriptstyle 0}$ = 50 au will statistically remain on their initial state regardless the encounter distance. Yet, variances show that high eccentric motion up to 0.27 can occur. Increasing $a_{\scriptscriptstyle 0}$ will drastically increase the rate of disrupted binaries, even for large encounter distances. We emphasize that changing the secondary star's initial orbital eccentricity and inclination will statistically lead to similar results. Besides, as planetary formation already takes place when stars are still member of their birth cluster, we show that Jupiter- and Saturn-like planets will necessarily have their initial orbit perturbed. We highlight two particular outcomes according to the binary's separation: either giant planets migrate, increase their eccentricity and remain on planar orbits (for $a_{\scriptscriptstyle 0}$ = 50 au) or they remain on their current location on circular orbit but with high orbital inclinations (for $a_{\scriptscriptstyle 0}\,\ge$ 100 au). We conclude that this in turn can affect terrestrial planet formation and the water transport from icy objects towards the circumprimary habitable zone.