Simulations of multiple nova eruptions induced by wind accretion in symbiotic systems

Abstract

We use a combined binary evolution code including dynamical effects to study nova eruptions in a symbiotic system. Following the evolution, over $\sim10^5$ years, of multiple consecutive nova eruptions on the surface of a $1.25 M_\odot$ white dwarf (WD) accretor, we present a comparison between simulations of two types of systems. The first is the common, well known, cataclysmic variable (CV) system in which a main sequence donor star transfers mass to its WD companion via Roche-lobe overflow. The second is a detached, widely separated, symbiotic system in which an asymptotic giant branch donor star transfers mass to its WD companion via strong winds. For the latter we use the Bondi-Hoyle-Lyttleton prescription along with orbital dynamics to calculate the accretion rate. We use the combined stellar evolution code to follow the nova eruptions of both simulations including changes in mass, accretion rate and orbital features. We find that while the average accretion rate for the CV remains fairly constant, the symbiotic system experiences distinct epochs of high and low accretion rates. The examination of epochs for which the accretion rates of both simulations are similar, shows that the evolutionary behaviors are identical. We obtain that for a given WD mass, the rate that mass is accreted ultimately determines the development, and that the stellar class of the donor is of no significance to the development of novae. We discuss several observed systems and find that our results are consistent with estimated parameters of novae in widely separated symbiotic systems.