Download or read book Three dimensional Non local Thermodynamic Equilibrium Radiative Transfer and Oxygen Abundances in Late type Stars written by Anish Mayur Amarsi and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The chemical compositions of the atmospheres of late-type stars, as inferred from stellar spectroscopic analyses, provide vital clues to unravelling the history of stars, galaxies, and the cosmos as a whole. However, the vast majority of stellar spectroscopic analyses make at least two assumptions that severely limit their accuracy: that stellar atmospheres are one-dimensional (1D) and hydrostatic; and that the material in the line-forming regions is in local thermodynamic equilibrium (LTE). Real atmospheres of late-type stars have convective envelopes that require a 3D time-evolving hydrodynamical treatment, and also real atmospheres are generally not in LTE. In this thesis I develop tools for 3D non-LTE radiative transfer calculations in late-type stars, and use them to address two outstanding problems that are pertinent to oxygen, which is one of the most important elements in astronomy. First is the so-called solar mod- elling problem, wherein inferences about the structure of the Sun based on helioseismology are in significant disagreement with those inferences based on the current best estimate of the solar chemical composition (as deduced from spectroscopy) and standard solar interior models. It has been strongly argued in the literature that a higher solar oxygen abundance is needed to resolve this problem. Second is the so-called oxygen problem in metal-poor stars, wherein different oxygen abundance diagnostics give different oxygen abundances in metal-poor Milky Way disk and halo stars. In particular, this has meant that the Galactic [O/Fe] versus [Fe/H] trend, a key tracer of chemical evolution, is poorly constrained in the metal-poor regime. I present new 3D non-LTE analyses of oxygen and silicon lines in the solar spectrum. The inferred solar oxygen and silicon abundances, 8.70 ± 0.03 dex and 7.51 ± 0.03 dex respectively, are consistent with the current canonical values to within errors, so maintaining the status quo on the solar modelling problem. I also present 3D non-LTE spectra for atomic oxygen lines across a grid of 3D hydrodynamic model atmospheres. Such a grid facilitates 3D non-LTE analyses of stars other than the Sun. With this grid I present analyses of the [O/Fe] versus [Fe/H] trend from Galactic disk and halo stars, and I demonstrate that with accurate stellar parameters and 3D non-LTE modelling, concordant results can be achieved between the two key atomic oxygen diagnostics: the [Oi]630nm line, and the Oi 777 nm lines. Lastly, I present a 3D non-LTE analysis of Fe i and Fe ii lines in four metal- poor benchmark stars: HD84937, HD122563, HD140283, and G64-12. I demonstrate that the 3D non-LTE iron abundances are typically 0.1 dex higher than the corresponding 1D non-LTE iron abundances. 3D effects of this order need to be accounted for if the Galactic [O/Fe] versus [Fe/H] relationship is to be properly constrained.
Download or read book Radiative Transfer in Stellar and Planetary Atmospheres written by Lucio Crivellari and published by Cambridge University Press. This book was released on 2020-01-09 with total page 251 pages. Available in PDF, EPUB and Kindle. Book excerpt: An essential overview of the physical and mathematical background of radiative transfer, and its applications to stellar and planetary atmospheres.
Download or read book Spectral Line Formation written by John T. Jefferies and published by . This book was released on 1968 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this book is to discuss certain aspects of the theory of the formation and analysis of the line spectrum of a hot gas. The underlying motivation for most of the studies discussed here lies in a desire to develop a physically sound procedure for interpreting the line spectrum of a stellar atmosphere ; correspondingly, the major emphasis is given to problems encountered in astrophysics.
Download or read book Departures from Local Thermodynamic Equilibrium in an AO i e A0 Star Atmosphere written by Myron Lecar and published by . This book was released on 1964 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Theory of Stellar Atmospheres written by Ivan Hubeny and published by Princeton University Press. This book was released on 2014-10-26 with total page 944 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most authoritative synthesis of the quantitative spectroscopic analysis of stellar atmospheres This book provides an in-depth and self-contained treatment of the latest advances achieved in quantitative spectroscopic analyses of the observable outer layers of stars and similar objects. Written by two leading researchers in the field, it presents a comprehensive account of both the physical foundations and numerical methods of such analyses. The book is ideal for astronomers who want to acquire deeper insight into the physical foundations of the theory of stellar atmospheres, or who want to learn about modern computational techniques for treating radiative transfer in non-equilibrium situations. It can also serve as a rigorous yet accessible introduction to the discipline for graduate students. Provides a comprehensive, up-to-date account of the field Covers computational methods as well as the underlying physics Serves as an ideal reference book for researchers and a rigorous yet accessible textbook for graduate students An online illustration package is available to professors at press.princeton.edu
Download or read book Stars and Stellar Processes written by Mike Guidry and published by Cambridge University Press. This book was released on 2019-02-07 with total page 573 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents the physics of stars in relation to modern topics such as neutrino oscillations, supernovae, black holes, and gravitational waves.
Download or read book Non LTE Effects on Oxygen Abundance Determinations for Solar type Stars written by Dan Kiselman and published by . This book was released on 1991 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Stellar Astrophysics written by Roger John Tayler and published by Taylor & Francis Group. This book was released on 1992 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stellar Astrophysics contains a selection of high-quality papers that illustrate the progress made in research into the structure and evolution of stars. Senior undergraduates, graduates, and researchers can now be brought thoroughly up to date in this exciting and ever-developing branch of astronomy.
Download or read book The Atmosphere and Climate of Mars written by Robert M. Haberle and published by Cambridge University Press. This book was released on 2017-06-29 with total page 613 pages. Available in PDF, EPUB and Kindle. Book excerpt: Humanity has long been fascinated by the planet Mars. Was its climate ever conducive to life? What is the atmosphere like today and why did it change so dramatically over time? Eleven spacecraft have successfully flown to Mars since the Viking mission of the 1970s and early 1980s. These orbiters, landers and rovers have generated vast amounts of data that now span a Martian decade (roughly eighteen years). This new volume brings together the many new ideas about the atmosphere and climate system that have emerged, including the complex interplay of the volatile and dust cycles, the atmosphere-surface interactions that connect them over time, and the diversity of the planet's environment and its complex history. Including tutorials and explanations of complicated ideas, students, researchers and non-specialists alike are able to use this resource to gain a thorough and up-to-date understanding of this most Earth-like of planetary neighbours.
Download or read book New Worlds New Horizons in Astronomy and Astrophysics written by National Research Council and published by National Academies Press. This book was released on 2011-02-04 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Driven by discoveries, and enabled by leaps in technology and imagination, our understanding of the universe has changed dramatically during the course of the last few decades. The fields of astronomy and astrophysics are making new connections to physics, chemistry, biology, and computer science. Based on a broad and comprehensive survey of scientific opportunities, infrastructure, and organization in a national and international context, New Worlds, New Horizons in Astronomy and Astrophysics outlines a plan for ground- and space- based astronomy and astrophysics for the decade of the 2010's. Realizing these scientific opportunities is contingent upon maintaining and strengthening the foundations of the research enterprise including technological development, theory, computation and data handling, laboratory experiments, and human resources. New Worlds, New Horizons in Astronomy and Astrophysics proposes enhancing innovative but moderate-cost programs in space and on the ground that will enable the community to respond rapidly and flexibly to new scientific discoveries. The book recommends beginning construction on survey telescopes in space and on the ground to investigate the nature of dark energy, as well as the next generation of large ground-based giant optical telescopes and a new class of space-based gravitational observatory to observe the merging of distant black holes and precisely test theories of gravity. New Worlds, New Horizons in Astronomy and Astrophysics recommends a balanced and executable program that will support research surrounding the most profound questions about the cosmos. The discoveries ahead will facilitate the search for habitable planets, shed light on dark energy and dark matter, and aid our understanding of the history of the universe and how the earliest stars and galaxies formed. The book is a useful resource for agencies supporting the field of astronomy and astrophysics, the Congressional committees with jurisdiction over those agencies, the scientific community, and the public.
Download or read book Stellar Structure and Evolution written by Rudolf Kippenhahn and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: A complete and comprehensive treatment of the physics of the stellar interior and the underlying fundamental processes and parameters. The text presents an overview of the models developed to explain the stability, dynamics and evolution of the stars, and great care is taken to detail the various stages in a star's life. The authors have succeeded in producing a unique text based on their own pioneering work in stellar modeling. Since its publication, this textbook has come to be considered a classic by both readers and teachers in astrophysics. This study edition is intended for students in astronomy and physics alike.
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1975 with total page 1550 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modern Methods in Collisional Radiative Modeling of Plasmas written by Yuri Ralchenko and published by Springer. This book was released on 2016-02-25 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a compact yet comprehensive overview of recent developments in collisional-radiative (CR) modeling of laboratory and astrophysical plasmas. It describes advances across the entire field, from basic considerations of model completeness to validation and verification of CR models to calculation of plasma kinetic characteristics and spectra in diverse plasmas. Various approaches to CR modeling are presented, together with numerous examples of applications. A number of important topics, such as atomic models for CR modeling, atomic data and its availability and quality, radiation transport, non-Maxwellian effects on plasma emission, ionization potential lowering, and verification and validation of CR models, are thoroughly addressed. Strong emphasis is placed on the most recent developments in the field, such as XFEL spectroscopy. Written by leading international research scientists from a number of key laboratories, the book offers a timely summary of the most recent progress in this area. It will be a useful and practical guide for students and experienced researchers working in plasma spectroscopy, spectra simulations, and related fields.
Download or read book Saturn in the 21st Century written by Kevin H. Baines and published by Cambridge University Press. This book was released on 2019 with total page 495 pages. Available in PDF, EPUB and Kindle. Book excerpt: A detailed overview of Saturn's formation, evolution and structure written by eminent planetary scientists involved in the Cassini Orbiter mission.
Download or read book Physics of the Interstellar and Intergalactic Medium written by Bruce T. Draine and published by Princeton University Press. This book was released on 2010-12-20 with total page 560 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is a comprehensive and richly illustrated textbook on the astrophysics of the interstellar and intergalactic medium--the gas and dust, as well as the electromagnetic radiation, cosmic rays, and magnetic and gravitational fields, present between the stars in a galaxy and also between galaxies themselves. Topics include radiative processes across the electromagnetic spectrum; radiative transfer; ionization; heating and cooling; astrochemistry; interstellar dust; fluid dynamics, including ionization fronts and shock waves; cosmic rays; distribution and evolution of the interstellar medium; and star formation. While it is assumed that the reader has a background in undergraduate-level physics, including some prior exposure to atomic and molecular physics, statistical mechanics, and electromagnetism, the first six chapters of the book include a review of the basic physics that is used in later chapters. This graduate-level textbook includes references for further reading, and serves as an invaluable resource for working astrophysicists. Essential textbook on the physics of the interstellar and intergalactic medium Based on a course taught by the author for more than twenty years at Princeton University Covers radiative processes, fluid dynamics, cosmic rays, astrochemistry, interstellar dust, and more Discusses the physical state and distribution of the ionized, atomic, and molecular phases of the interstellar medium Reviews diagnostics using emission and absorption lines Features color illustrations and detailed reference materials in appendices Instructor's manual with problems and solutions (available only to teachers)
Download or read book Physics Briefs written by and published by . This book was released on 1994 with total page 1256 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Astrophysics for Physicists written by Arnab Rai Choudhuri and published by Cambridge University Press. This book was released on 2010-03-11 with total page 491 pages. Available in PDF, EPUB and Kindle. Book excerpt: Designed for teaching astrophysics to physics students at advanced undergraduate or beginning graduate level, this textbook also provides an overview of astrophysics for astrophysics graduate students, before they delve into more specialized volumes. Assuming background knowledge at the level of a physics major, the textbook develops astrophysics from the basics without requiring any previous study in astronomy or astrophysics. Physical concepts, mathematical derivations and observational data are combined in a balanced way to provide a unified treatment. Topics such as general relativity and plasma physics, which are not usually covered in physics courses but used extensively in astrophysics, are developed from first principles. While the emphasis is on developing the fundamentals thoroughly, recent important discoveries are highlighted at every stage.
