The effects of star-gas interactions on binary evolution in open clusters

TL;DR

This study investigates how star-gas interactions, especially negative dynamical friction, influence the dynamical evolution and binary populations in open clusters through direct N-body simulations.

Contribution

It introduces the role of negative dynamical friction from star-gas interactions in altering cluster expansion and binary evolution, using detailed simulations.

Findings

NDF enhances cluster expansion and star redistribution.

Binary neutron star-main sequence systems decline more rapidly.

NDF retains binaries with larger semi-major axes and lower eccentricities.

Abstract

Star-gas interactions can provide gravitational feedback that influences the dynamical evolution of stellar clusters, through processes such as dynamical friction (DF) and its non-dissipative counterpart, negative dynamical friction (NDF). Using the \texttt{PeTar} code, we perform direct $N$-body simulations of an open cluster initially containing $10^4$ stars, evolving within a gaseous medium spanning a range of ambient densities. Our results demonstrate that NDF associated with stellar outflows interacting with the surrounding gas can enhance the rate of cluster expansion, preferentially transporting stars toward the cluster outskirts. This behavior is accompanied by a more rapid decline in the number of binaries composed of a neutron star and a main-sequence star. A statistical analysis of binary orbital parameters further indicates that, compared to DF-dominated evolution, NDF tends to retain systems with larger semi-major axes and lower eccentricities. Outflow-ambient gas interactions can modify the dynamical processing of binaries in star clusters, leading to changes in the survival fraction and composition of the remaining binary population.