Nemesis encounters of nearby Hipparcos stars

Very close encounters of stars might lead to significant perturbations of their Oort-type clouds, planetesimal belts and planetary systems. We have calculated encounter parameters of Hipparcos stars using HIP2, Pulkovo and CRVAD2 catalogs of radial velocities. It turns out that some stars have encounters within 0.1 pc from each other and might be on an essential collision course up to few thousands AU. We present here examples with accurate astrometric data and stable with respect to errors of radial velocities within $\pm 0.3$ km/s. They include $\beta$ vs. $\gamma$ Virginis, 61 Cygni vs. $\chi^1$ Orionis as well as close encounters involving $\eta$ Bo\"otis, AB Doradus, 61 Urs{\ae} Majoris and others.