# USco1606-1935: An Unusually Wide Low-Mass Triple System?

## TL;DR

This study investigates a candidate ultrawide, low-mass triple system in Upper Scorpius, providing detailed observations and analysis to assess its physical association and implications for wide binary formation.

## Contribution

It offers the first detailed characterization of USco1606-1935, highlighting its potential as an unusually wide low-mass multiple system and emphasizing the need for systematic searches in young associations.

## Key findings

- Both components are young, comoving members of Upper Scorpius.
- High-resolution observations reveal the primary is a close binary.
- There is a 25% probability of at least one similar wide pair in the association.

## Abstract

We present photometric, astrometric, and spectroscopic observations of USco160611.9-193532 AB, a candidate ultrawide (~1600 AU), low-mass (M_tot~0.4 M_sun) multiple system in the nearby OB association Upper Scorpius. We conclude that both components are young, comoving members of the association; we also present high-resolution observations which show that the primary is itself a close binary system. If the Aab and B components are gravitationally bound, the system would fall into the small class of young multiple systems which have unusually wide separations as compared to field systems of similar mass. However, we demonstrate that physical association can not be assumed purely on probabilistic grounds for any individual candidate system in this separation range. Analysis of the association's two-point correlation function shows that there is a significant probability (25%) that at least one pair of low-mass association members will be separated in projection by <15", so analysis of the wide binary population in Upper Sco will require a systematic search for all wide systems; the detection of another such pair would represent an excess at the 98% confidence level.