Dynamical evolution of second-generation circumstellar/protoplanetary disks in evolved wide binary systems

Abstract

In mass-transferring wide binary stellar systems, the companion star can capture some of the mass released in wind by the primary evolved star, and form an accretion disk. Such accretion disks could evolve to form disks of comparable properties to protoplanetary disks and may enable the formation of new planets and/or the interactions, re-growth, and re-migration of pre-existing planets in the newly formed disks. We study the formation and the dynamical evolution of such "second generation" (SG) protoplanetary disks in evolved wide binary systems, with primaries in the mass range of 1-8 Solar mass. We follow their evolution from the asymptotic giant branch (AGB) phase of the red giant stellar donor until its evolution to become a white dwarf. We perform 1D semi-analytical numerical simulations for several binary systems varying the mass of the evolved stellar donor and the initial orbital distance, taking into account the changing mass-loss rates and the binary orbital expansion due to mass-loss. We calculate the radial density profile of the formed SG accretion disk and its temperature profile, considering a non-stationary viscosity profile which depends on the radial temperature profile. We find that SG circumstellar disks evolve to form a long-lived stable structure over the lifetime of the donor star, and we show that we can consistently produce the observed conditions and accretion rate inferred for the Mira evolved wide-binary system. The quasi-steady state radial surface density profiles are comparable with the typical range of masses and densities of observed (regular "first-generation") protoplanetary disks. This suggests that realistic SG disks can give rise to a second phase of planet formation and dynamics in old wide binary systems.