Relativistic Binaries in Globular Clusters

Galactic globular clusters are old, dense star systems typically containing 10\super{4}--10\super{7} stars. As an old population of stars, globular clusters contain many collapsed and degenerate objects. As a dense population of stars, globular clusters are the scene of many interesting close dynamical interactions between stars. These dynamical interactions can alter the evolution of individual stars and can produce tight binary systems containing one or two compact objects. In this review, we discuss theoretical models of globular cluster evolution and binary evolution, techniques for simulating this evolution that leads to relativistic binaries, and current and possible future observational evidence for this population. Our discussion of globular cluster evolution will focus on the processes that boost the production of hard binary systems and the subsequent interaction of these binaries that can alter the properties of both bodies and can lead to exotic objects. Direct {\it N}-body integrations and Fokker--Planck simulations of the evolution of globular clusters that incorporate tidal interactions and lead to predictions of relativistic binary populations are also discussed. We discuss the current observational evidence for cataclysmic variables, millisecond pulsars, and low-mass X-ray binaries as well as possible future detection of relativistic binaries with gravitational radiation.Comment: 88 pages, 13 figures. Submitted update of Living Reviews articl

The gravitational billion body problem : Het miljard deeltjes probleem

The increased availability of accelerator technology in modern supercomputers forces users to redesign their algorithms. These accelerators are specifically designed to offer huge amounts of parallel compute power. In this thesis I show how to harness the power of these parallel processors for astrophysical simulations. I start with an introduction that presents the developments in astrophysical algorithms and used hardware since the 1960__s till today. In the following scientific chapters I discuss the use of GPU accelerator technology for direct N-body methods and for the more advanced hierarchical algorithms. These advanced algorithms are more complex to implement on large parallel architectures, but by redesigning the algorithms it is possible to take advantage of the GPU. The developed algorithms are applied to simulate galaxy mergers to explain discrepancies in observational results. In the simulations we test different merger configurations and try to match the results with observational data. The final chapter shows how to scale the developed software code to thousands of GPUs as available in the Titan supercomputer. The in this thesis developed and presented algorithms allow astronomers to take advantage of the new GPU technology and thereby run simulations that contain thousand times more particles than was possible beforeNWOUBL - phd migration 201