Encounters between single and binary stars - The effect of intruder mass on the maximum impact velocity for which the mean change in binding energy is positive

Abstract

view Abstract Citations (36) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Encounters between Single and Binary Stars: The Effect of Intruder Mass on the Maximum Impact Velocity for Which the Mean Change in Binding Energy is Positive Hills, J. G. Abstract A close encounter between a binary and an intruder will, on average, increase the orbital binding energy of the binary if the impact velocity V is below some critical value VE. It will decrease it if V > VE. The folklore that this crossover velocity VE is the critical velocity VHS separating hard binaries from soft binaries is false. (Hard binaries have enough binding energy for the total energy of the three-star system to be negative.) VE is found to depend on the ratio of the mass of the intruder to the mass of the binary components. In the case of equally massive binary components, only if all three stars are equally massive does VE ≍ VHS. In close encounters with low-mass intruders, the binding energy decreases even when the impact velocity of the intruder is an order of magnitude less than VHS. VE increases to nearly 4 VHS for intruders ten times as massive as the binary components. It then increases gradually to nearly 10 VHS for intruders 104 times as massive as the binary components. Vorbital, the initial orbital velocity in the pre-encounter binary, is: a better approximation to VE than is VHS. VE is within a factor of 2 of Vorbital if the intruder is less than 100 times as massive as the binary components. VE increases to about 5Vorbital for intruders l04 times as massive as the binary components. These results suggest that it is much better to speak of the "slow-intruder" limit and the "fast-intruder" limit when gauging if an encounter will cause the binding energy of the binary orbit to increase or decrease rather than the customary "hard-binary" and "soft-binary" limits. A binary will increase its binding energy in en- counters in the slow-intruder limit and decrease it in the fast-intruder limit. Publication: The Astronomical Journal Pub Date: March 1990 DOI: 10.1086/115388 Bibcode: 1990AJ.....99..979H Keywords: Binary Stars; Binding; Stellar Mass; Stellar Orbits; Encounters; Stellar Motions; Astrophysics; STARS: BINARIES full text sources ADS |