The seminar will be held online

1) Speaker: D.A. Kovaleva (INASAN)

Title:  “Collinder 135 and UBC 7: A physical pair of open clusters”

Abstract: 

Given the closeness of the two open clusters Collinder 135 and UBC 7 on the sky, we investigate the possibility that the two clusters are physically related. We aim to recover the present-day stellar membership in the open clusters situated at 300 pc from the Sun in order to constrain their kinematic parameters, ages, and masses and to restore their primordial phase space configuration. Numerical simulations use the integration of cluster trajectories backwards in time. As a result, we constrain the age, spatial coordinates, velocities, radii, and masses of the clusters. We estimate the actual separation of the cluster centres equal to 24 pc. The orbital integration shows that the clusters were much closer in the past if their current line-of-sight velocities are very similar and the total mass is more than seven times larger than the mass of the most reliable members. We conclude that the two clusters might very well have formed a physical pair based on the observational evidence as well as numerical simulations. The probability of a chance coincidence is only about 2%. Further, we investigate wide surroundings of the clusters and approaches for further insight into their dynamical history.