Low-mass binary millisecond pulsars (LMBPs) are born with very small orbital eccentricities, typically of order e_i ～ 10~(-6)-10~(-3). In globular clusters, however, higher eccentricities e_f e_i can be induced by dynamical interactions with passing stars. Here we show that the cross section for this process is much larger than previously estimated. This is because, even for initially circular binaries, the induced eccentricity e_f for an encounter with pericenter separation r_p beyond a few times the binary semimajor axis a declines only as a power law, e_f ∝(r_p/a)~(-5/2), and not as an exponential. We find that all currently known LMBPs in clusters were probably affected by interactions, with their current eccentricities typically greater than at birth by an order of magnitude or more.
展开▼
