A New Open Cluster Census in the Region of Cygnus OB2 with Gaia Data

We revisit the Cygnus OB2 region to perform a detailed open cluster census taking profit from the high accuracy of Gaia DR3 astrometric and photometric data. HDBSCAN clustering algorithm is applied to the five astrometric parameters ($\alpha$ , $\delta$ , ${\mu }_{\alpha }\cos \delta$ , ${\mu }_{\delta }$ , $？$ ) in a circular region centred at $\left(l\mathrm{,}b\right)=\left({79.8}^{°}\mathrm{,}+{0.8}^{°}\right)$ of radius 1.5？ up to $G=19.5$ mag and leads us to detect four unnoticed open clusters named RSL-03, RSL-04, RSL-05 and RSL-06, as well as 20 known clusters. The mean proper motion of the open clusters is determined and the members are identified. The coordinates of the centre of the clusters and radii are calculated and their distances are estimated. The analysis of the mean proper motion and the distance of Bica 1, Bica 2, FSR 0236, FSR 0238, FSR 0224, HSC 625, OC-123, OC-128, NGC 6910, RSL-04, RSL-05, and RSL-06 suggests that these open clusters would be related to Cyg OB2 association. This is the first time that Bica 1 and Bica 2 have been identified using the Gaia DR3 five astrometric parameters. Besides, the open cluster HSC 630 would be related to the Left over-density found by our working group in a previous paper as an association candidate.