(Sub)stellar companions shape the winds of evolved stars

TL;DR

This paper investigates how binary interactions influence the shaping of stellar winds in evolved stars, revealing that such interactions lead to nonspherical morphologies in AGB stars and planetary nebulae, supported by ALMA observations.

Contribution

It introduces an evolutionary scenario linking binary interactions to the nonspherical shapes of AGB stars and planetary nebulae, based on ALMA observations.

Findings

AGB star winds show nonspherical geometries similar to planetary nebulae.

Morphology and mass-loss rate are correlated in AGB stars.

Binary interactions likely drive the observed wind shaping.

Abstract

Binary interactions dominate the evolution of massive stars, but their role is less clear for low- and intermediate-mass stars. The evolution of a spherical wind from an asymptotic giant branch (AGB) star into a nonspherical planetary nebula (PN) could be due to binary interactions. We observed a sample of AGB stars with the Atacama Large Millimeter/submillimeter Array (ALMA) and found that their winds exhibit distinct nonspherical geometries with morphological similarities to planetary nebulae (PNe). We infer that the same physics shapes both AGB winds and PNe; additionally, the morphology and AGB mass-loss rate are correlated. These characteristics can be explained by binary interaction. We propose an evolutionary scenario for AGB morphologies that is consistent with observed phenomena in AGB stars and PNe.