Testing the binary hypothesis for the formation and shaping of planetary nebulae

TL;DR

This paper reviews evidence supporting the Binary Hypothesis, which suggests that binary companions are essential for shaping and forming planetary nebulae, based on observed higher binary fractions in their central stars.

Contribution

It provides a review of current observational results indicating a higher binary fraction in planetary nebulae central stars compared to main sequence stars, supporting the binary formation hypothesis.

Findings

Binary fraction in central stars is higher than in main sequence stars.

Photometric variability and infrared excess suggest a significant binary presence.

Results support the idea that many planetary nebulae form through binary interactions.

Abstract

There is no quantitative theory to explain why a high 80% of all planetary nebulae are non-spherical. The Binary Hypothesis states that a companion to the progenitor of a central star of planetary nebula is required to shape the nebula and even for a planetary nebula to be formed at all. A way to test this hypothesis is to estimate the binary fraction of central stars of planetary nebulae and to compare it with that of the main sequence population. Preliminary results from photometric variability and the infrared excess techniques indicate that the binary fraction of central stars of planetary nebulae is higher than that of the main sequence, implying that PNe could preferentially form via a binary channel. This article briefly reviews these results and current studies aiming to refine the binary fraction.