Dynamics of stellar wind in a Roche potential: implications for (i) outflows & periodicities relevant to astronomical masers, and (ii) generation of baroclinicity

TL;DR

This paper investigates stellar wind dynamics in binary systems, revealing how periodic density variations cause maser intensity fluctuations, explain bipolar outflows, and generate baroclinicity that could seed magnetic fields.

Contribution

It demonstrates the link between binary-induced wind modulations and observed maser periodicities, bipolar outflows, and baroclinicity generation through numerical simulations.

Findings

Maser intensity varies periodically with binary period.

Flow velocity structure remains stable over time.

Baroclinicity is generated, potentially seeding magnetic fields.

Abstract

We study the dynamics of stellar wind from one of the bodies in the binary system, where the other body interacts only gravitationally. We focus on following three issues: (i) we explore the origin of observed periodic variations in maser intensity; (ii) we address the nature of bipolar molecular outflows; and (iii) we show generation of baroclinicity in the same model setup. From direct numerical simulations and further numerical modelling, we find that the maser intensity along a given line of sight varies periodically due to periodic modulation of material density. This modulation period is of the order of the binary period. Another feature of this model is that the velocity structure of the flow remains unchanged with time in late stages of wind evolution. Therefore the location of the masing spot along the chosen sightline stays at the same spatial location, thus naturally explaining the observational fact. This also gives an appearance of bipolar nature in the standard position-velocity diagram, as has been observed in a number of molecular outflows. Remarkably, we also find the generation of baroclinicity in the flow around binary system, offering another site where the seed magnetic fields could possibly be generated due to the Biermann battery mechanisms, within galaxies.