Dynamical evolution of second-generation circumstellar/protoplanetary discs 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 disc. We study the formation and the dynamical evolution of such ‘second generation’ (SG) protoplanetary discs in evolved wide binary systems, with primaries in the mass range of 1–8 solar masses. 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 $\Sigma (t,r)$ profile of the formed SG accretion disc and its temperature profile $T(t,r)$, considering a non-stationary viscosity profile $\nu (t,r)$ which depends on the radial temperature profile. We find that SG circumstellar discs evolve to form long-lived massive structures 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.