Entering the Wind Roche Lobe Overflow realm in Symbiotic Systems

TL;DR

This study uses dynamical simulations to explore wind accretion and orbital evolution in symbiotic systems, revealing the significance of Wind Roche Lobe Overflow, tidal forces, and the potential for systems to reach the Chandrasekhar limit.

Contribution

It introduces a multi-level physical modeling approach to analyze wind accretion regimes and orbital dynamics in symbiotic binaries, highlighting the role of tides and drag forces.

Findings

Systems alternate between wind accretion and WRLO regimes during high mass-loss phases.

Tidal forces lead to orbital shrinkage and increased accretion efficiency.

High-mass WDs in massive systems can reach the Chandrasekhar limit.

Abstract

We present a suite of dynamical simulations designed to explore the orbital and accretion properties of compact (2$-$7 AU) symbiotic systems, focusing on wind accretion, drag forces, and tidal interactions. Using three levels of physical complexity, we model systems of accreting white dwarfs (WDs) with masses of 0.7, 1.0, and 1.2 M$_\odot$ orbiting evolving Solar-like stars with 1, 2, and 3 M$_\odot$. We show that systems alternate between standard wind accretion and Wind Roche Lobe Overflow (WRLO) regimes during periods of high mass-loss rate experienced by the donor star (the peak of red giant phase and/or thermal pulses). For some configurations, the standard wind accretion has mass accretion efficiencies similar to those obtained by WRLO regime. Tidal forces play a key role in compact systems, leading to orbital shrinkage and enhanced accretion efficiency. We find that systems with high-mass WDs ($\geq 1$ M$_\odot$) and massive donors (2$-$3 M$_\odot$) are the only ones to reach the Chandrasekhar limit. Interestingly, the majority of our simulations reach the Roche lobe overflow condition that is not further simulated given the need of more complex hydrodynamical simulations. Our analysis shows that increasing physical realism, by including drag and tides, systematically leads to more compact final orbital configurations. Comparison with compact known symbiotic systems seems to suggest that they are very likely experiencing orbital decay produced by tidal forces.