Explosive ejections generated by gravitational interactions

TL;DR

This paper presents an analytical model and simulations showing how high-velocity stellar encounters can gravitationally accelerate cluster particles, causing explosive ejections, with application to the Orion BN/KL region.

Contribution

It introduces a novel analytical framework for understanding explosive ejections caused by stellar interactions, supported by numerical simulations and applied to real astrophysical phenomena.

Findings

Cluster particles are gravitationally accelerated by high-velocity stars.

Explosive outflows can result from gravitational interactions in stellar clusters.

Model successfully explains the Orion Fingers' explosive outflow.

Abstract

During the fragmentation and collapse of a molecular cloud, it is expected to have close encounters between (proto)stellar objects that can lead to the ejection of a fraction of them as runaway objects. However, the duration and the consequences of such encounters perhaps are small such that there is no direct evidence of their occurrence. As a first approximation, in this work, we analytically analyze the interaction of a massive object that moves at high velocity into a cluster of negligible mass particles with an initial number density distribution $\propto R^{-\alpha}$. We have found that the runaway conditions of the distribution after the encounter are related to the mass and the velocity of the star and the impact parameter of each particle to the stellar object. Then, the cluster particles are gravitationally accelerated by the external approaching star, destroying the cluster and the dispersion and velocities of the particles have explosive characteristics. We compare this analytical model with several numerical simulations and finally, we applied our results to the Orion Fingers in the Orion BN/KL region, which show an explosive outflow that could be triggered by the gravitational interaction of several (proto)stellar objects.