3 research outputs found
The role of radial migration in open cluster and field star populations with Gaia dr3
The survival time of a star cluster depends on its total mass, density, and
thus size, as well as on the environment in which it was born and in which
lies. Its dynamical evolution is influenced by various factors such as
gravitational effects of the Galactic bar, spiral structures, and molecular
clouds. Overall, the factors that determine the longevity of a cluster are
complex and not fully understood. This study aims to investigate if open
clusters and field stars respond differently to the perturbations that cause
radial migration. In particular, we aim at understanding the nature of the
oldest surviving clusters. We compared the time evolution of the kinematic
properties of two Gaia DR3 samples: the first sample is composed of 40
open clusters and the second one of 66,000 MSTO field stars. Both
selected samples are composed of stars selected with the same quality
criterion, belonging to the thin disc, in a similar metallicity range, located
in the same Galactocentric region [7.5-9 kpc] and with ages >1 Gyr. We
performed a statistical analysis comparing the properties of the samples of
field stars and of open clusters. A qualitative comparison of kinematic and
orbital properties reveals that clusters younger than 2-3 Gyr are more
resistant to perturbations than field stars and they move along quasi-circular
orbits. Conversely, clusters older than approximately 3 Gyr have more eccentric
and inclined orbits than isolated stars in the same age range. Such orbits lead
them to reach higher elevations on the Galactic plane, maximising their
probability to survive several Gyr longer. A formal statistical analysis
reveals that there are differences among the time evolution of most of the
kinematic and orbital properties of field stars and open clusters. Our results
suggest that oldest survived clusters are usually more massive and move on
orbits with higher eccentricity.Comment: 13 pages, 20 figures, 2 tables. Article accepted for publication in
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The Abundance of S-Process Elements: Temporal and Spatial Trends from Open Cluster Observations
Spectroscopic observations of stars belonging to open clusters, with well-determined ages and distances, are a unique tool for constraining stellar evolution, nucleosynthesis, mixing processes, and, ultimately, Galactic chemical evolution. Abundances of slow (s) process neutron capture elements in stars that retain their initial surface composition open a window into the processes that generated them. In particular, they give us information on their main site of production, i.e., the low-and intermediate-mass Asymptotic Giant Branch (AGB) stars. In the present work, we review some observational results obtained during the last decade that contributed to a better understanding of the AGB phase: the growth of s-process abundances at recent epochs, i.e., in the youngest stellar populations; the different relations between age and [s/Fe] in distinct regions of the disc; and finally the use of s-process abundances combined with those of α elements, [s/α], to estimate stellar ages. We revise some implications that these observations had both on stellar and Galactic evolution, and on our ability to infer stellar ages