Close binarity as an outburst trigger among surveyed eruptive stars

Determine whether the eruptive star systems Z CMa, XZ Tau, FU Ori, V960 Mon, NY Ori, and EX Lup host close binary companions with separations less than 10 au that could act as triggers for their outbursts, noting that only UZ Tau E is known to be a spectroscopic binary and the presence of similarly close companions in the other systems is not established.

Background

The survey finds that most of the observed eruptive systems are multiple, but the companions are generally widely separated. Theory suggests that if binarity is a primary trigger for outbursts, the effect should be strongest in close binary systems, typically with separations less than about 10 au.

While UZ Tau E is confirmed as a spectroscopic (close) binary, the existence of similarly close companions for the other surveyed eruptive stars remains unconfirmed. Establishing whether such close companions exist is critical to assessing the binarity-trigger hypothesis and requires high-resolution or spectroscopic observations to probe the innermost regions around these stars.

References

As pointed out by , if binarity was the main trigger of the outburst, it would happen preferably in close binary systems (i.e. less than 10$\,$au). Apart from UZ~Tau, which is a spectroscopic binary, {this is not known to be the case} for all the other systems.

— The environment around young eruptive stars. SPHERE/IRDIS polarimetric imaging of 7 protostars (2403.12124 - Zurlo et al., 18 Mar 2024) in Section 5.3, Multiplicity (label s:multi)