Surveying Planetary Nebulae Central Stars for Close Binaries: Constraining Evolution of Central Stars Based on Binary Parameters

Todd Hillwig

doi:10.3390/galaxies6030085

Abstract

The increase in discovered close binary central stars of planetary nebulae is leading to a sufficiently large sample to begin to make broader conclusions about the effect of close binary stars on common envelope evolution and planetary nebula formation. Herein I review some of the recent results and conclusions specifically relating close binary central stars to nebular shaping, common envelope evolution off the red giant branch, and the total binary fraction and double degenerate fraction of central stars. Finally, I use parameters of known binary central stars to explore the relationship between the proto-planetary nebula and planetary nebula stages, demonstrating that the known proto-planetary nebulae are not the precursors of planetary nebulae with close binary central stars.

Highlights

The study of binary stars in planetary nebulae (PNe) has the potential to provide information about the formation of PNe and the evolution of the central stars (CSs)
central stars of planetary nebulae (CSPNe) can tell us about the evolution of PNe with close binary nuclei, especially in the context of proto-planetary nebulae (PPNe)
grazing envelope evolution (GEE) is a more recent theory and does not have the volume of work performed at this time, and it is not clear that it can result in short-period systems with separations of a few R or less [15]

Summary

Introduction

The study of binary stars in planetary nebulae (PNe) has the potential to provide information about the formation of PNe and the evolution of the central stars (CSs). Photometric surveys looking for variability due to a companion tend to find close binary systems with orbital periods of about a week or less (e.g., [1,2,3]) Such photometric surveys are sensitive to both cool companions and double degenerate systems [4,5]. Close binary CSPNe with a main sequence companion have light curves dominated by an irradiation effect in which the inner hemisphere of the cool star is irradiated and heated by the hot CS. This behavior results in a nearly sinusoidal light curve with one maximum and one minimum per orbit. CSPNe can tell us about the evolution of PNe with close binary nuclei, especially in the context of proto-planetary nebulae (PPNe)

The Connection between Central Binaries and PN Shaping

The CE Phase and Evolution of the CS

Companions to Binary CSPNe and the Close Binary Fraction

The Relationship between PPNe and PNe

Discussion