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arXiv · 2206.03777

Unraveling UBC 274: a morphological, kinematical and chemical analysis of a disrupting open cluster

L. Casamiquela·J. Olivares·Y. Tarricq·S. Ferrone·C. Soubiran·P. Jofré·P. di Matteo·F. Espinoza-Rojas·A. Castro-Ginard·D. de Brito Silva·J. Chanamé
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Abstract

We do a morphological, kinematic and chemical analysis of the disrupting cluster UBC 274 (2.5 Gyr, $d=1778$ pc) to study its global properties. We use HDBSCAN to obtain a new membership list up to 50 pc from its centre and up to magnitude $G=19$ using Gaia EDR3 data. We use high resolution and high signal-to-noise spectra to obtain atmospheric parameters of 6 giants and subgiants, and individual abundances of 18 chemical species. The cluster has a highly eccentric (0.93) component, tilted $\sim$10 deg with respect to the plane of the Galaxy, which is morphologically compatible with the result of a test-particle simulation of a disrupting cluster. Our abundance analysis shows that the cluster has a subsolar metallicity of [Fe/H]$=-0.08\pm0.02$. Its chemical pattern is compatible with that of Ruprecht 147, of similar age but located closer to the Sun, with the remarkable exception of neutron-capture elements, which present an overabundance of $[n\mathrm{/Fe]}\sim0.1$. The cluster's elongated morphology is associated with the internal part of its tidal tail, following the expected dynamical process of disruption. We find a significant sign of mass segregation where the most massive stars appear 1.5 times more concentrated than other stars. The cluster's overabundance of neutron-capture elements can be related to the metallicity dependence of the neutron-capture yields due to the secondary nature of these elements, predicted by some models. UBC 274 presents a high chemical homogeneity at the level of $0.03$ dex in the sampled region of its tidal tails.

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L. Casamiquela, J. Olivares, Y. Tarricq, S. Ferrone, C. Soubiran, P. Jofré, P. di Matteo, F. Espinoza-Rojas, A. Castro-Ginard, D. de Brito Silva, J. Chanamé. 2022-06-08. Unraveling UBC 274: a morphological, kinematical and chemical analysis of a disrupting open cluster. https://doi.org/10.1051/0004-6361%2F202243658

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