Establish whether the multiple VLBA source pairs are gravitationally bound

Establish whether the four multiple VLBA source pairs identified within the same image in the Orion Nebula Cluster are gravitationally bound systems.

Background

The survey identifies four source pairs detected within the same image: ONC177, ONC413, ONC414, and ONC427. Their projected separations range from approximately 6 to 65 AU, making physical multiplicity plausible, but projected separation alone does not establish gravitational binding.

The paper indicates that the astrometric information needed to resolve the question will be addressed in a future astrometry paper. Thus, the gravitational status of these systems remains explicitly unresolved in the present variability analysis.

References

We note it is currently unknown whether these sources are gravitationally bound. These sources will be discussed in more detail in a future astrometry paper.

— A VLBA survey of radio stars in the Orion Nebula Cluster: III. Inter-epoch variability analysis  (2609.26466 - O'Kelly et al., 22 Sep 2026) in Section 4, Results and Discussion, paragraph describing multiple VLBA sources associated with one phase centre

While the nature of this source remains unclear, near-infrared analysis by indicates that this source is a close pair of low-mass stars.

— A VLBA survey of radio stars in the Orion Nebula Cluster: III. Inter-epoch variability analysis  (2609.26466 - O'Kelly et al., 22 Sep 2026) in Section 4.2, Radio Variability, paragraph discussing ONC441