Encounter Phenomena in Triple Stars

A series of numerical integrations has been performed to study the encounter of a binary system with a third body. The model assumes coplanar orbits and point masses, with the third body encountering the binary on a parabolic orbit. Twenty-three special and 197 random orbits were considered. Capture is possible if the initial periastron distance of the parabolic orbit is less than 6 times the semimajor axis of the binary. The lifetimes of such systems may be very long, suggesting that a few of the observed wide multiple or trapezium systems may be transient capture phenomena. There is a slight suggestion that such an encounter may tend to increase the eccentricity of the orbit of the remaining binary.