The role of binarity in Wolf-Rayet central stars of planetary nebulae

TL;DR

This paper investigates the role of binary interactions in the formation of Wolf-Rayet central stars of planetary nebulae, highlighting the scarcity of known [WR] binaries and their unique properties compared to typical post-common-envelope binaries.

Contribution

It provides new insights into the binary characteristics of [WR] central stars, emphasizing their rarity and distinct orbital properties compared to other post-CE binaries.

Findings

Few [WR] binaries are known, with only two confirmed post-CE systems.

[WR] central stars tend to lack main sequence companions.

Evidence suggests the existence of wider binaries that could host [WR] stars.

Abstract

Over a hundred planetary nebulae (PNe) are known to have H-deficient central stars that mimic the spectroscopic appearance of massive Wolf-Rayet stars. The formation of these low-mass Wolf-Rayet stars, denoted [WR] stars, remains poorly understood. While several binary formation scenarios have been proposed, there are too few [WR] binaries known to determine their feasibility. Out of nearly 50 post-common-envelope (post-CE) binary central stars known, only PN G222.8$-$04.2 ([WC7], $P=1.26$ d) and NGC 5189 ([WO1], $P=4.05$ d) have a [WR] component. The available data suggests that post-CE central stars with [WR] components lack main sequence companions and have a wider orbital separation than typical post-CE binaries. There is also some indirect evidence for wide binaries that could potentially lead to the discovery of more [WR] binaries.