Identifying and characterising post-encounter disintegrating system

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2023-07

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Universidad de Valparaíso

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Facultad de Ciencias, Instituto de Física y Astronomía

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Disintegrating multiple systems are thought to be very common based on numerical simulations, which predict that 50% to 95% of non-hierarchical triple systems and 10% of hierarchical triple systems undergo an ejection at some point in their evolution. However, very few of these systems have so far been observed. Kinematic studies of the Hipparcos catalogue have revealed only 10 disintegrating triple candidates. They are presumably the result of dynamical encounters taking place in the Galactic disk between single/multiple systems. In this thesis, I expanded the search for such systems to study their properties, as well as to characterize possible low-mass ejecta (i.e. brown dwarfs and planets). I have assembled a list of 20 candidate systems using astrometry from the Tycho-Gaia astrometric solution (later upgraded with Gaia DR3), and here I present the follow-up of 9 of them. I have obtained medium-resolution spectra for 4 of them and used the spectra to determine their radial velocity and metallicity. These measurements allowed me to conclude that two of the systems observed with ISIS are likely genuine disintegrating systems, for which I have reconstructed the most probable interaction scenario. I have obtained DECam imaging for 5 systems and by combining near-infrared photometry and proper motion, I searched for ultra- cool ejected components. I found that the system consisting of TYC 7731-1951-1, TYC 7731-2128-1 AB, and TYC 7731-1995-1ABC?, contains one very promising ultra-cool dwarf candidate. Using additional data from the literature, I have found that 3 out of the 5 disintegrating system candidates observed with DECam are likely to be true dis- integrating systems. Overall, this thesis demonstrates the feasibility of searching for disintegrating multiple systems with the method described, as well as the feasibility of identifying additional low-mass ejected components. Future Gaia data releases and upcoming large area near-infrared surveys and new space telescopes (e.g. LSST, EU- CLID, SPHEREX, NEOSurveyor) will enable me to search for even larger samples of disintegrating systems and more low-mass ejecta. This population will be fundamental to observationally constrain the rate at which this type of systems interact in the Galactic disk. The fundamental importance of searching for possible disintegrating multiple systems is its contribution in providing further constraints to the formation models of binaries and multiple systems and their evolution.

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ESTRELLAS MULTIPLES, ASTROMETRIA

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