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

doi:10.1093/mnras/stad071

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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 open clusters (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 giant molecular cloud. 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.