# On the triple-star origin of the planetary nebula Sh 2-71

## TL;DR

This paper explores the hypothesis that the planetary nebula Sh 2-71 originated from a triple star system that has since disintegrated, supported by observational evidence and orbital simulations.

## Contribution

It presents new observational features aligned with a proposed tertiary orbit and tests the triple-star formation hypothesis for Sh 2-71.

## Key findings

- Discovery of emission regions aligned with the proposed tertiary orbit
- Support for the triple-star formation scenario based on stellar properties
- Numerical orbital integrations consistent with the triple hypothesis

## Abstract

Recent studies have indicated that triple star systems may play a role in the formation of an appreciable number of planetary nebulae, however only one triple central star is known to date (and that system is likely too wide to have had much influence on the evolution of its component stars). Here, we consider the possibility that Sh 2-71 was formed by a triple system which has since broken apart. We present the discovery of two regions of emission, seemingly aligned with the proposed tertiary orbit (i.e. in line with the axis formed by the two candidate central star systems previously considered in the literature). We also perform a few simple tests of the plausibility of the triple hypothesis based on the observed properties (coordinates, radial velocities, distances and proper motions) of the stars observed close to the projected centre of the nebula, adding further support through numerical integrations of binary orbits responding to mass loss. Although a number of open questions remain, we conclude that Sh 2-71 is currently one of the best candidates for planetary nebula formation influenced by triple-star interactions.