Effect of Intruder Mass on Collisions with Hard Binaries. I. Zero-Impact Parameter

Over 57,000 close encounters between hard binaries with orbital eccentricities of e(0) = 0, 2/3, and 0.99 and intruders whose masses range from M(i) = 0.001 to 100,000 times the mass M(0) of the binary components were simulated. The probability of an exchange collision in close encounters increases from 0 for M(i)/M(0) less than 0.2 to unity for M(i)/M(0) = 3-70 and gradually drops to about 90 percent for M(i)/M(0) greater than 70. The orbital binding energy increases nearly linearly with M(i)/M(0) for small M(i)/M(0). It saturates at about four times the preencounter value for M(i)/M(0) = 3-100 before increasing monotonically with increasing M(i) to over 60 times its preencounter value for M(i)/M(0) = 100,000. The probability of an orbital resonance peaks sharply at about 95 percent for M(i)/M(0) = 0.55 if e(0) = 0. It is about 40 percent for very small M(i)/M(0) and 5 percent for very large M(i)/M(0).