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The binary content of multiple populations in NGC 3201

S. Kamann, B. Giesers, N. Bastian, J. Brinchmann, S. Dreizler, F. Göttgens, T.-O. Husser, M. Latour, P. M. Weilbacher, L. Wisotzki

We investigate the binary content of the two stellar populations that coexist in the globular cluster NGC 3201. Previous studies of binary stars in globular clusters have reported higher binary fractions in their first populations (P1, having field-like abundances) compared to their second populations (P2, having anomalous abundances). This is interpreted as evidence for the latter forming more centrally concentrated. In contrast to previous studies, our analysis focusses on the cluster centre, where comparable binary fractions between the populations are predicted because of short relaxation times. However, we find that even in the centre of NGC 3201, the observed binary fraction of P1 is higher (23.1 ± 6.2)% compared to (8.2 ± 3.5)% in P2. Our results are difficult to reconcile with a scenario in which the populations only differ in their initial concentrations, but instead suggests that the populations also formed with different fractions of binary stars.

binaries: spectroscopic; techniques: radial velocities; globular clusters: individual: NGC 3201; stars: abundances; Astrophysics - Solar and Stellar Astrophysics; Astrophysics - Astrophysics of Galaxies

Astronomy & Astrophysics
Volume 635, Article Number A65, Number of pages 6
2020 March

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia