Letter to the Editor

On the formation of runaway stars BN and x in the Orion Nebula Cluster

¹ Dept. of Space, Earth & Environment, Chalmers University of Technology, Gothenburg, Sweden
e-mail: juan.farias@chalmers.se
² Dept. of Astronomy, University of Virginia, Charlottesville, VA 22904, USA

Received: 15 December 2017
Accepted: 30 March 2018

Abstract

We explore scenarios for the dynamical ejection of stars BN and x from source I in the Kleinmann-Low nebula of the Orion Nebula Cluster (ONC), which is important because it is the closest region of massive star formation. This ejection would cause source I to become a close binary or a merger product of two stars. We thus consider binary-binary encounters as the mechanism to produce this event. By running a large suite of N-body simulations, we find that it is nearly impossible to match the observations when using the commonly adopted masses for the participants, especially a source I mass of 7 M_⊙. The only way to recreate the event is if source I is more massive, that is, ~20 M_⊙. However, even in this case, the likelihood of reproducing the observed system is low. We discuss the implications of these results for understanding this important star-forming region.