Binary open clusters in the Gaia data

TL;DR

This study uses Gaia data to identify and analyze binary open clusters in the Milky Way, discovering new pairs and confirming that clusters born in groups tend to be young, with some pairs sharing members or forming stellar complexes.

Contribution

The paper presents a method to identify truly binary open clusters using Gaia data, discovering new binary pairs and analyzing their properties in the Milky Way.

Findings

Approximately ten pairs are likely the same clusters sharing members.

Fourteen pairs are possibly true binaries, including five newly discovered.

Two clusters are part of the stellar complex LISCA I.

Abstract

Context. Observations indicate that the fraction of potential binary star clusters in the Milky Way is either the same or lower than that of the Magellanic Clouds. The unprecedented precision in the parallax measurements by Gaia has allowed for the discovery of a growing number of new binary open clusters (OCs). Aims. We aim to survey the candidates of truly binary open clusters that are formed simultaneously, using information from the Gaia database. Methods. Based on the most recent catalog of open clusters, we investigated the interactions of adjacent binary open clusters in our Galaxy within separations of 50 pc. We compared their coordinates, proper motions, parallaxes, and color-magnitude diagrams(CMDs) via binary plots for all candidate pairs. The candidates of truly binary open clusters are selected on the basis of their common proper motions and consistent behaviors in the CMDs of different clusters that are limited to a separation of 50 pc. Results. About ten pairs of the selected binary open clusters appear to be the same clusters, based on evidence that almost half ofthe cluster members are shared. Fourteen pairs are possibly true binaries, implying that they may come from the same clouds, among which five pairs are newly discovered. In addition, two clusters, UBC 46 and UBC 192, were found to be part of the stellar complex LISCA I. Our results confirm that OCs born in groups are usually composed of young open clusters.