The Proper Motions of the Double Radio Source n in the Orion BN/KL Region

TL;DR

This study extends the proper motion observations of radio sources in the Orion BN/KL region over 22.5 years, confirming their outward movement from a common point and revealing a new plasma ejection event in source n.

Contribution

It provides improved proper motion measurements and confirms the past close approach of sources BN and I, also identifying a recent plasma ejection in source n.

Findings

Sources BN, I, and n are moving away from a common origin.

The closest approach of BN and I was around the year 1475.

Source n shows a new plasma ejection after 2006.36.

Abstract

We have extended the time baseline for observations of the proper motions of radio sources in the Orion BN/KL region from 14.7 to 22.5 years. We present improved determinations for the sources BN and I. In addition, we address the proper motions of the double radio source n, that have been questioned in the literature. We confirm that all three sources are moving away at transverse velocities of tens of km s$^{-1}$ from a region in-between them, where they were located about 500 years ago. Source n exhibits a new component that we interpret as due to a one-sided ejection of free-free emitting plasma that took place after 2006.36. We used the highly accurate relative proper motions between sources BN and I to determine that their closest separation took place in the year 1475$\pm$6, when they were within $\sim$100 AU or less from each other in the plane of the sky.