# A catalog of wide binary and multiple systems of bright stars from Gaia-DR2 and the Virtual Observatory

## TL;DR

This paper presents a new catalog of 3,741 bright comoving binary and multiple star systems identified from Gaia-DR2 data, emphasizing the reliability of the methodology and the importance of accurate system identification for stellar studies.

## Contribution

The study introduces a robust method for identifying wide binary systems from Gaia-DR2, reducing false positives compared to previous catalogs, and provides a publicly available, reliable catalog of these systems.

## Key findings

- Identified 3,741 candidate systems with separations from 400 to 500,000 au.
- Validated the methodology by recovering known star clusters.
- Found previous catalogs contained many false systems and could not confirm ultra-wide binaries.

## Abstract

Binary and multiple stars have long provided an effective empirical method of testing stellar formation and evolution theories. In particular, the existence of wide binary systems (separations $>$20,000 au) is particularly challenging to binary formation models as their physical separations are beyond the typical size of a collapsing cloud core ($\sim$5,000$-$10,000 au). We mined the recently published Gaia-DR2 catalog to identify bright comoving systems in the five-dimensional space (sky position, parallax, and proper motion). We identified 3,741 comoving binary and multiple stellar candidate systems, out of which 575 have compatible RVs for all the members of the system. The candidate systems have separations between $\sim$400 and 500,000 au. We used the analysis tools of the Virtual Observatory to characterize the comoving system members and to assess their reliability. The comparison with previous comoving systems catalogs obtained from TGAS showed that these catalogs contain a large number of false systems. In addition, we were not able to confirm the ultra-wide binary population presented in these catalogs. The robustness of our methodology is demonstrated by the identification of well known comoving star clusters and by the low contamination rate for comoving binary systems with projected physical separations $<$50,000 au. These last constitute a reliable sample for further studies. The catalog is available online at the Spanish Virtual Observatory portal (http://svo2.cab.inta-csic.es/vocats/v2/comovingGaiaDR2/).