Download or read book The Winds of B Supergiants written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-06-19 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present the most suitable data sets available in the International Ultraviolet Explorer (IUE) archive for the study of time-dependent stellar winds in early B supergiants. The UV line profile variability in 11 B0 to B3 stars is analyzed, compared and discussed, based on 16 separate data sets comprising over 600 homogeneously reduced high-resolution spectrograms. The targets include 'normal' stars with moderate rotation rates and examples of rapid rotators. A gallery of grey-scale images (dynamic spectra) is presented, which demonstrates the richness and range of wind variability and highlights different structures in the winds of these stars. This work emphasizes the suitability of B supergiants for wind studies, under-pinned by the fact that they exhibit unsaturated wind lines for a wide range of ionization. The wind activity of B supergiants is substantial and has highly varied characteristics. The variability evident in individual stars is classified and described in terms of discrete absorption components, spontaneous absorption, bowed structures, recurrence, and ionization variability and stratification. Similar structures can occur in stars of different fundamental parameters but also different structures may occur in the same star at a given epoch. We discuss the physical phenomena that may be associated with the spectral signatures, and highlight the challenges that these phenomena present to theoretical studies of time-dependent outflows in massive stars. In addition, SEI line-synthesis modelling of the UV wind lines is used to provide further information about the state of the winds in our program stars. Typically the range, implied by the line profile variability, in the product of mass-loss rate and ion fraction (M qi) is a factor of approximately 1.5, when integrated between 0.2 and 0.9 v infinity; it it can however be several times larger over localized velocity regions. At a given effective temperature the mean relative ion ratios can differ by a f
Download or read book Understanding Stellar Evolution written by Henny J. G. L. M. Lamers and published by CRC Press. This book was released on 2018-02-28 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: 'Understanding Stellar Evolution' is based on a series of graduate-level courses taught at the University of Washington since 2004, and is written for physics and astronomy students and for anyone with a physics background who is interested in stars. It describes the structure and evolution of stars, with emphasis on the basic physical principles and the interplay between the different processes inside stars such as nuclear reactions, energy transport, chemical mixing, pulsation, mass loss, and rotation. Based on these principles, the evolution of low- and high-mass stars is explained from their formation to their death. In addition to homework exercises for each chapter, the text contains a large number of questions that are meant to stimulate the understanding of the physical principles. An extensive set of accompanying lecture slides is available for teachers in both Keynote(R) and PowerPoint(R) formats.
Download or read book B e Stars written by Anne Marie Hubert and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: The idea of having a meeting came to the Editors when working on several aspects of galactic Be and B[e] stars. They found that a general summary of the properties of B[e] stars was missing, so that the organiza tion of a first meeting on these objects appeared as very useful. B[e] stars have hydrogen line emission and forbidden [Fe 11] and [0 I] emission lines in their spectra; they are also characterized by a strong IR excess due to circumstellar dust. Having a large amount of extinction in the UV and the visual they have been less frequently observed than other emission line objects. Although about one hundred galactic objects have been classified as B[e], only fif teen or so have been studied in some detail. Besides this, the evolutionary status of these objects is rat her controversial, are they pre-main sequence or stars on the way to become nUclei of planetary nebulae? Other difficult problems appear when considering the relations of these stars with other similar groups, like Herbig AeBe stars, Be, luminous blue variables and the superluminous B[e] stars observed in the Magellanic Clouds. The conference seems timely since large surveys like DENIS and 2Mass, plus new space and new instruments for the micron, millimeter and cen timeter wavelength region will result in the discovery of more stars of this group.
Download or read book Luminous Stars in Nearby Galaxies written by Roberta M. Humphreys and published by MDPI. This book was released on 2020-12-10 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt: Studies on the populations of luminous stars in nearby resolved galaxies have revealed a complex distribution in the luminosity–temperature plane (the HR diagram). The fundamentals of massive star evolution are mostly understood, but the roles of mass loss, episodic mass loss, rotation, and binarity are still in question. Moreover, the final stages of these stars of different masses and their possible relation to each other are not understood. The purpose of this volume is to provide a current review of the different populations of evolved massive stars. The emphasis is on massive stars in the Local Group, the Magellanic Clouds, and the nearby spirals M31 and M33.
Download or read book Massive Stars written by Space Telescope Science Institute (U.S.). Symposium and published by Cambridge University Press. This book was released on 2009-11-12 with total page 253 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents observational and theoretical papers from world experts addressing the important role in astrophysics of massive stars.
Download or read book Instability and Variability of Hot Star Winds written by Anthony F.J. Moffat and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 475 pages. Available in PDF, EPUB and Kindle. Book excerpt: This specialized workshop was conceived during the workshop on "Non isotropic and Variable Outflows from Stars", which was held at the Space Telescope Science Institute in October, 1991. At that meeting, the four of us collectively decided that the time was ripe for an even more focussed discussion of the basic issues in the area of hot-star wind instability and its observable manifestations. Not that the big problems have been solved! Rather, we are currently in a phase of rapid development, both with regard to the models and to the observations. The key issue at this new workshop would be to decide how the time-dependent structures observed in hot-star winds (e. g. , NACs, DACs, blobs, clumps, filaments, shells, puffs, jets, etc. ) relate to radiative and other instabilities. Further questions concern the role of turbulence and the nature of its driver, and the effect of stellar rotation, pulsation, and magnetic fields on time-dependent phenomena in hot-star winds. Of no less importance is the impact of stellar wind variability on the derivation of mass-loss rates, on stellar evolution, and on momentum/energy deposition in the interstellar medium. To attain our goal of maximum confrontation (in the positive sense!) we decided: (1) to limit the workshop to the observers and theoreticians most active in this field in the world; (2) to insist that virtually all participants present a talk, thereby avoiding the distraction of poster sessions; and (3) to allocate approximately half of the allotted time to discussion.
Download or read book Cyclical Variability in Stellar Winds written by Lex Kaper and published by Springer Science & Business Media. This book was released on 2013-06-05 with total page 426 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is well known that stellar winds are variable, and the fluctuations are often cyclical in nature. This property seems to be shared by the winds of cool and hot stars, even though their outflows are driven by fundamentally different physical mechanisms. Since very similar models have been proposed to explain the cyclical wind variations observed in a wide variety of stars, the time was ripe for astrophysicists from many different sub-disciplines to present the state of the art in a concise form. The proceedings will provide a useful, up-to-date overview of the observations, interpretation, and modelling of the time-dependent mass outflows from all sorts of stars.
Download or read book Massive Stars as Cosmic Engines IAU S250 written by International Astronomical Union. Symposium and published by Cambridge University Press. This book was released on 2008-07-17 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reviews our current understanding of the life, evolution and death of massive stars; for researchers and graduate students.
Download or read book Foundations of Radiation Hydrodynamics written by Dimitri Mihalas and published by Courier Corporation. This book was released on 2013-04-10 with total page 752 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excellent, informative volume focuses on dynamics of nonradiating fluids, problems involving waves, shocks and stellar winds, physics of radiation, radiation transport, and the dynamics of radiating fluids. 1984 edition.
Download or read book Physics of the Sun written by P.A. Sturrock and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 293 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume, together with its two companion volumes, originated in a study commis sioned by the United States National Academy of Sciences on behalf of the National Aeronautics and Space Administration. A committee composed of Tom Holzer, Dimitri Mihalas, Roger Ulrich and myself was asked to prepare a comprehensive review of current knowledge concerning the physics of the sun. We were fortunate in being able to persuade many distinguished scientists to gather their forces for the preparation of 21 separate chapters covering not only solar physics but also relevant areas of astrophysics and solar-terrestrial relations. It proved necessary to divide the chapters into three separate volumes that cover three different aspects of solar physics. Volumes 1 and 2 are concerned with 'The Solar Interior' and with 'The Solar Atmosphere'. This volume, devoted to 'Astrophysics and Solar-Terrestrial Relations', focuses on problems of solar physics from these two different but complementary perspectives. The emphasis throughout these volumes is on identifying and analyzing the relevant physical processes, but each chapter also contains a great deal of descriptive material. In preparing our material, the authors and editors benefited greatly from the efforts of a number of scientists who generously agreed to review individual chapters. I wish therefore to take this opportunity to thank the the following individuals for this valuable contribution to our work: S. K. Antiochos, E. H. Avrett, J. N. Bahcall, C. A. Barnes, G. Bicknell, D. Black, M. L. Blake, P. Bodenheimer, F. H. Busse, R. C. Canfield, T. R.
Download or read book The Century of Space Science written by J.A. Bleeker and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 1819 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the most attractive features of the young discipline of Space Science is that many of the original pioneers and key players involved are still available to describe their field. Hence, at this point in history we are in a unique position to gain first-hand insight into the field and its development. To this end, The Century of Space Science, a scholarly, authoritative, reference book presents a chapter-by-chapter retrospective of space science as studied in the 20th century. The level is academic and focuses on key discoveries, how these were arrived at, their scientific consequences and how these discoveries advanced the thoughts of the key players involved. With over 90 world-class contributors, such as James Van Allen, Cornelis de Jager, Eugene Parker, Reimar Lüst, and Ernst Stuhlinger, and with a Foreword by Lodewijk Woltjer (past ESO Director General), this book will be immensely useful to readers in the fields of space science, astronomy, and the history of science. Both academic institutions and researchers will find that this major reference work makes an invaluable addition to their collection.
Download or read book Angular Momentum and Mass Loss for Hot Stars written by L.A. Willson and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamental unsolved problems of stellar astrophysics include the effects of angular momentum on stellar structure and evolution, the nature and efficiency of the processes by which angular momentum is redistributed within and lost from stars, and the role that stellar rotation plays in enhancing or driving stellar mass loss. There appears to be a qualitative change in the nature and efficiency of these mechanisms near spectral type FO: hotter (more massive) stars typically retain more angular momentum at least until they reach the main sequence, while cooler stars typically spin down quickly. For the hotter stars, recent work suggests a strong link between the type of pulsation behavior, the mass loss rates, and the rotation velocity. If the same mechanisms are able to drive mass loss from the main sequence A stars, as has recently been proposed, then the current interpretations of a number of observations will be drastically affected: e. g. the ages of clusters may be incorrect by up to a factor of two, and the surface abundances of isotopes of He, Li and Be may no longer give constraints on cosmological nucleosynthesis. There are also effects on the evolution of the abundances of elements in the interstellar medium and on the general evolution of populations of stars. Thus the questions of the mechanisms of angular momentum and mass loss of stars more massive than the sun is important not only for stellar studies but for the foundations of much of modern astrophysics.
Download or read book Mass Outflows from Stars and Galactic Nuclei written by Luciana Bianchi and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 427 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this workshop was to put together observational and theoretical works on outflows from different kinds of astrophysical objects, occurring on different scales and at various evolutionary phases, and to discuss the impact of observations from future space missions. For the stars, we thought to follow throughout the evolution the relevance (rates and dynamical rrodes) of the mass loss phenomenon, e. g. to explain how and when massive stars loose most of their ini tial mass to end up with typical WD masses. The observations of the solar wind were included for being a unique case where the origin and propagation of the outflow can be resolved. We thought that the comparison with similar phenomena occurring in galactic outflows would be fruitful, as demonstrated by recent works on galactic winds and jets. The interest of having this workshop in Torino came because there are groups in this area, at the Astronomical Observatory and at the Institute of Physics of the University, involved in the theoretical and observational studies of outflows from astrophysical objects. The members of the Scientific Organizing Conmi ttee were: V. Castellani, C. Cesarski, P. Conti, A. Ferrari, A. Gabriel, M. Grewing, Y. Kondo, H. Lamers, V. Manno, M. Rees and R. Schilizzi. The Local Organizing Conmi ttee was: L. Bianchi, G. Massone and E. Antonucci. During the workshop the following topics were treated: the solar wind, the mass loss from cool stars and from hot stars (m. s.
Download or read book A Concise History of Solar and Stellar Physics written by Jean-Louis Tassoul and published by Princeton University Press. This book was released on 2014-10-05 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive overview of the history of ideas about the sun and the stars, from antiquity to modern times. Two theoretical astrophysicists who have been active in the field since the early 1960s tell the story in fluent prose. About half of the book covers most of the theoretical research done from 1940 to the close of the twentieth century, a large body of work that has to date been little explored by historians. The first chapter, which outlines the period from about 3000 B.C. to 1700 A.D., shows that at every stage in history human beings have had a particular understanding of the sun and stars, and that this has continually evolved over the centuries. Next the authors systematically address the immense mass of observations astronomy accumulated from the early seventeenth century to the early twentieth. The remaining four chapters examine the history of the field from the physicists perspective, the emphasis being on theoretical work from the mid-1840s to the late 1990s--from thermodynamics to quantum mechanics, from nuclear physics and magnetohydrodynamics to the remarkable advances through to the late 1960s, and finally, to more recent theoretical work. Intended mainly for students and teachers of astronomy, this book will also be a useful reference for practicing astronomers and scientifically curious general readers.
Download or read book Clumping in Hot star Winds written by Wolf-Rainer Hamann and published by Universitätsverlag Potsdam. This book was released on 2008 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Literature 1980 Part 2 written by Siegfried Böhme and published by Springer Science & Business Media. This book was released on 2013-04-18 with total page 851 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Introduction to Stellar Winds written by Henny J. G. L. M. Lamers and published by Cambridge University Press. This book was released on 1999-06-17 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first comprehensive introduction to the observations and theories of stellar winds; a long-awaited graduate textbook, written by two founders of the field.
