Planetary Nebulae Principles & Paradigms: Binaries, Accretion, Magnetic Fields

TL;DR

This paper explores how binary interactions and accretion processes drive the formation of aspherical outflows in planetary nebulae, emphasizing the role of magnetic fields and accretion dynamics in shaping observed outflows.

Contribution

It presents a unified view of magnetohydrodynamic outflow models, distinguishes launch and propagation regimes, and highlights the significance of accretion onto white dwarfs from stellar companions.

Findings

Outflows are consistent with accretion onto white dwarfs in depleting envelopes.

Magnetized accretion disks produce similar outflow predictions across models.

Binary interactions are crucial for shaping planetary nebulae outflows.

Abstract

Observations suggest that many, if not all, post AGB systems evolve through an aspherical outflow phase. Such outflows require a sufficient engine rotational energy which binaries can provide. Via common envelope evolution, binaries can directly eject equatorial outflows or produce poloidal outflows from magnetized accretion disks around the primary or secondary. We discuss how accretion driven magnetohydrodynamic outflow models all make similar predictions for the outflow power and speed and we distinguish between the launch vs. propagation regimes of such outflows. We suggest that the high velocity bipolar outflows observed in planetary nebulae (PNe) and the lower velocity but higher power bipolar outflows observed in pre-PNe (pPNe) are kinematically consistent with time dependent accretion onto a white dwarf (WD) within a depleting envelope. Since the WD primary core is always present in all post-AGB systems, accretion onto this core is potentially common. Previous work has focused on core accretion from sub-stellar companions, but low mass stellar companions may be more important, and further work is needed.