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This thesis by Cole Johnston brings novel insights into the inner workings of young massive stars. By bridging the observational fields of binary stars and asteroseismology this thesis uses state of the art statistical techniques to scrutinise theories of modern stellar astrophysics. Developing upon the commonly used isochrone fitting methodology, the author introduces the idea of isochrone cloud fitting in order to account for the full breadth of physics observed in stars. The author combines this methodology with gravity mode asteroseismic analysis to asses the level of chemical mixing deep within the stellar core in order to determine the star‘s age and core mass. Wrapped into a robust statistical framework to account for correlations, this methodology is employed to analyse individual stars, multiple systems, and clusters alike to demonstrate that chemical mixing has dramatic impact on stellar structure and evolution.
In this thesis, the hydrodynamics of massive star interiors are explored. Our primary theoretical tool is multi-dimensional hydrodynamic simulation using realistic initial conditions calculated with the one-dimensional stellar evolution code, TYCHO. The convective shells accompanying oxygen and carbon burning are examined, including models with single as well as multiple, simultaneously burning shells. A convective core during hydrogen burning is also studied in order to test the generality of the flow characteristics. Two and three dimensional models are calculated. We analyze the properties of turbulent convection, the generation of internal waves in stably stratified layers, and the rate and character of compositional mixing at convective boundaries.
An advanced review of how binary stars affect stellar evolution, presenting results from state-of-the art models and recent observations.
With the development of nuclear physics the theory of the stellar interior entered a new phase. Many new investigations have been conducted and the results published in a variety of specialized media. This book brings these results together in a single volume and summarizes the present status of the theory of stellar evolution. Originally published in 1958. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.
Understanding the formation of low- and high-mass stars is a fundamental challenge of modern astronomy. They form from the collapse of gravitationally-unstable cores, in the interstellar medium which is nothing but simple to model: energies of gravity, turbulence, magnetic fields, radiation, and cosmic-rays are close to equipartition. Hence, numerical simulations are of a great help in studying star formation. In this work, we have focused on the formation of massive stars, which are very luminous and power a strong radiative force which can, in a simple unidimensional view, stop further accretion of material. Multi-dimensional simulations and particular treatment of stellar radiation are two main ingredients. In that view, the main task of the present thesis has been the numerical coupling between two radiative transfer methods. With this new tool, we have focused on three axes: the mechanisms of accretion, of ejection, and the formation of multiple stellar systems.The very heart of this thesis has been the numerical coupling between two radiative transfer methods into the RAMSES code (Teyssier, 2002), and its validation through pure radiative transfer benchmark tests. Then, we have applied this method in a radiation-hydrodynamical context of a massive pre-stellar core collapse. We have shown that the radiative force is enhanced, in comparison to the previous method used, ending up in the formation of larger radiative cavities and slightly less accretion. More importantly, we have tested the presence and accretion via radiative Rayleigh-Taylor instabilities at the border of these cavities, whose existence was an active debate in the community. We have shown their absence in our simulations to be of physical, rather than numerical, origin.In an on-going side-project carried in collaboration with A. Oliva and R. Kuiper (Univ. of Tübingen), we have led a comparison study between our respective codes, when it comes to modelling accretion disk fragmentation and subsequent formation of multiple stellar systems. With a Cartesian grid (instead of their spherical grid), our results show the formation of a binary or triple system, while they obtained a single star. When a multiple system is sufficiently dominated in mass by a single object, our codes show correct agreement on the disk rotation profile and temperature structure.Finally, we have run original simulations of turbulent magnetized cores with ambipolar diffusion and the newly implemented hybrid radiative transfer method. We have identified the magnetic tower flow as the dominant outflow mechanism, except very close to the massive protostar where radiative force dominates. We have compared these outflow properties to those obtained from observational statistical samples. Our results tend to show a good agreement, provided our initial conditions are representative of the least massive progenitors of high-mass stars, and the collimation is not intrinsic to the outflow mechanism but also depends on environmental factors. Hence, these questions need to be further investigated. We have identified disk-mediated accretion as the only accretion mechanism, with disk sizes significantly smaller than predicted by the radiation-hydrodynamical simulations, and in agreement with recent low-mass star formation results. Eventually, we have questioned the disk-outflow-magnetic fields alignment. Our results are consistent with a random disk-magnetic field alignment and a slightly better outflow-magnetic field alignment, provided the medium is not too turbulent.
Red giant stars are evolutionarily advanced objects in the closing stages of their nuclear burning lifetime. Observed with increasing spectral coverage they display a variety of unusual phenomena. Many are characterized by peculiar (non-solar) surface chemical compositions which provide otherwise unobtainable clues to interior nucleosynthesis, mixing and evolution. Others may have received their chemical peculiarities by mass transfer from a companion. This book reports on the proceedings of the International Astronomical Union Colloquium 106. It contains discussions on many aspects of these stars, combining theory and observation to interpret these objects in terms of their evolutionary history. There are 20 review papers, 69 abstracts and short contributed papers and a complete transcript of the valuable summary panel discussion. Professional astronomers will find this book useful as a reference work which incorporates current research on the modelling and evolution of these unstable stars.
The 14th RCNP OSAKA International Symposium on Nuclear Reaction Dynamics of Nucleon-Hadron Many Body System was held in Osaka from December 6 to 9, 1995. The symposium covered current topics from Nucleon Spins and Mesons in Nuclei to Quark Lepton Nuclear Physics. Thus it included the field of hadron/nuclear physics from sub-GeV to multi-GeV energy region, as well as recent activities and development at RCNP. It was also intended to be a kind of winter school for young researchers/graduate students.This proceedings consists of the invited talks and lectures presented by leading physicists in the field and short oral presentations.
This book reviews the importance of massive stars in several areas of astrophysics. Massive stars are objects that are 10-100 times the mass of our Sun. Above ten solar masses, loss through stellar winds begins to have a major impact on the evolution of a star. The upper limit of 100 solar masses is derived from observations. Significant progress has now been achieved in massive star research. New models, along with high quality observations, have improved our understanding of the formation, structure, atmosphere, and evolution of these massive objects. They are formed in violent bursts of star formation and are probably related to the phenomena observed in active galactic nuclei. The workshop at the Space Telescope Science Institute examined the interplay between the astrophysics of massive stars and their location in extragalactic starburst regions. There are eighteen chapters by leading researchers. Each has been carefully edited to ensure that the book is a comprehensive introduction to the theory and observation of massive stars in starburst regions.
They range in size from microscopic particles to masses of many tons. The geologic diversity of asteroids and other rocky bodies of the solar system are displayed in the enormous variety of textures and mineralogies observed in meteorites. The composition, chemistry, and mineralogy of primitive meteorites collectively provide evidence for a wide variety of chemical and physical processes. This book synthesizes our current understanding of the early solar system, summarizing information about processes that occurred before its formation. It will be valuable as a textbook for graduate education in planetary science and as a reference for meteoriticists and researchers in allied fields worldwide.