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Spin alignment of stars in old open clusters

Enrico Corsaro
INAF Osservatorio Astrofisico di Catania

Stars originate by the gravitational collapse of a turbulent molecular cloud of a diffuse medium, and are often observed to form clusters. Stellar clusters therefore play an important role in our understanding of star formation and of the dynamical processes at play. However, investigating the cluster formation is difficult because the density of the molecular cloud undergoes a change of many orders of magnitude. Hierarchical-step approaches to decompose the problem into different stages are therefore required, as well as reliable assumptions on the initial conditions in the clouds. In this seminar I report on the use of the full potential of NASA Kepler asteroseismic observations coupled with 3D numerical simulations, to put for the first time strong constraints on the early formation stages of open clusters. Thanks to a Bayesian asteroseismic analysis of about 60 red giant members of NGC 6791 and NGC 6819, the two most populated open clusters observed in the nominal Kepler mission, a complete set of detailed oscillation mode properties for each star, with thousands of oscillation modes characterized, is obtained. I therefore show how these asteroseismic properties lead to a discovery about the rotation history of stellar clusters. Finally, the observational findings are compared with hydrodynamical simulations for stellar cluster formation to constrain the physical processes of turbulence, rotation, and magnetic fields that are in action during the collapse of the progenitor cloud into a proto-cluster. Some additional discussion on other more recent works presented in the literature will also be given.

2019 April 03, 13:30

Centro de Astrofísica da Universidade do Porto (Auditorium)
Rua das Estrelas, 4150-762 Porto

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