Secular chaos in white dwarf planetary systems: origins of metal pollution and short-period planetary companions

ABSTRACT Secular oscillations in multiplanet systems can drive chaotic evolution of a small inner body through non-linear resonant perturbations. This ‘secular chaos’ readily pushes the to an extreme eccentricity, triggering tidal interactions or collision with central star. We present numerical study secular chaos two planets and test particles using ring-averaging method, emphasis on relationship between planets’ properties time-scale efficiency diffusion. find that excite eccentricities time-scales spanning several orders magnitude given system. apply our results planetary around white dwarfs (WDs), specifically disruption high-eccentricity migration planetesimals planets. planetesimal belt driven by large (?10 M?), distant ($\gtrsim 10 \, \mathrm{au}$) sustain metal accretion WD over Gyr time-scales. constrain total mass initially within zone requiring predicted delivery rate Roche limit be consistent observed rates WDs atmospheric pollution throughout cooling sequence. Based occurrence long-period exoplanets exo-asteroid belts, we conclude significant (perhaps dominant) channel for polluting solitary WDs. also produce short-period concert various circularization mechanisms. discuss prospects detecting driving direct imaging microlensing.