Collimated Fast Winds in Wide Binary Progenitors of Planetary Nebulae

Abstract

We discuss the formation of planetary nebulae (PNe) having a pair of lobes, or multi-lobes, in their inner region surrounded by an elliptical or spherical shell or halo. We suggest that most of these PNe are formed by wide binary systems, with final orbital periods in the range of 40-10,000 years, such that there is no strong tidal interaction. The outer more spherical structure is formed from the early asymptotic giant branch (AGB) wind. Toward the end of the AGB the mass loss rate increases, and wind velocity possibly decreases, making the conditions for the formation of an accretion disk around the wide companion, more favorable. We assume that the accreting companion blows jets or a collimated fast wind (CFW), which lead to the formation of a pair of lobes in the inner region. In cases of a precessing accretion disk, a multi-lobes structure can be formed. We conduct a population synthesis study of such systems, and find that overall 5-20 percents of all PNe are formed by such binary systems. We also estimate that 20-40 percents of these systems possess observable departure from axisymmetry, e.g., the central star is not in the center of the nebula.