Dynamical friction on eccentric Keplerian trajectories

Location: class 315

We present an analytic approach to the dynamical friction (DF) acting on a compact astrophysical object moving on an eccentric Keplerian through a homogeneous and isotropic medium. The focus is on the orbit-averaged, steady-state dissipation rates of orbital energy and angular momentum. Using linear response theory, we derive results valid for arbitrary eccentricity, Mach number and environment. To validate  predictions with numerical simulations, we restrict ourselves to the case of an ideal fluid with negligible self-gravity. We demonstrate that, for a finite time perturbation switched on at t=0, a steady dissipation state is reached after a finite time bounded by twice the crossing time of the apocenter distance. We generalize our approach to binary perturbers, and compute the DF-induced orbital decay of a compact eccentric binary for a range of initial conditions and mass ratios.