Discovery and description of two young open clusters in the primordial group of NGC 6871

TL;DR

This study confirms a primordial group of young open clusters around NGC 6871 using Gaia DR3 data, identifying new members and analyzing their properties to understand their common origin and dispersal.

Contribution

It introduces the discovery of two new young open clusters within the primordial group of NGC 6871 and analyzes their properties and relationships.

Findings

Confirmed the primordial group containing at least six young open clusters.

Identified two new clusters, Casado 82 and Casado-Hendy 1, as members of this group.

Found that the group members are dispersing, with no true binary clusters except possibly Teutsch 8/FSR 198.

Abstract

A primordial group of open clusters containing NGC 6871 is confirmed and described through Gaia DR3 data and the previous literature. It is a star-forming complex containing at least six young OCs, including Teutsch 8, FSR 198 and Biurakan 2. Two nearby OCs (Casado 82 and Casado-Hendy 1) are newly identified and studied in detail and found to be also members of the cited group. The parameters of the components are sufficiently similar to postulate the case of at least six clusters born from a single GMC. None of the cluster pairs of the group seems to be an authentic binary cluster, with the possible exception of the candidate pair Teutsch 8/FSR 198. Instead, NGC 6871 seems to be disintegrating, and the primordial group members appear to be dispersing out rapidly. Searching for new open clusters in the vicinity of young or grouped OCs using Gaia data is an efficient strategy to find new associated OCs forming primordial groups.