Download or read book Observations and Theory of Pulsating Helium White Dwarfs written by Justin D. Steinfadt and published by . This book was released on 2011 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: Average C/O-core white dwarf stars pulsate in observable normal modes of oscillation with amplitudes of a few percent and periods of 100--1,000 seconds. As of this dissertation, no WD of less than 0.5 Msun has been observed to pulsate. White dwarfs of this low mass likely possess a He core and are products of very different stellar evolution. In this dissertation, we have constructed very low mass He-core WD models and predict the parameter space in which they may be observed to pulsate. We have also observed 13 stars, most of which are He-core WDs, in a search for the first He-core WD pulsator. While we were unsuccessful in discovering a pulsator, our detection limits offer unique constraints on He-core WD pulsation parameter space. As a fortuitous result of our pulsation search, we have discovered two unique eclipsing binary systems. One of these is the first eclipsing detached double white dwarf binary system offering the first opportunity to make model independent constraints on He-core WD models and evolution.
Download or read book White Dwarfs Advances in Observation and Theory written by M.A. Barstow and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 555 pages. Available in PDF, EPUB and Kindle. Book excerpt: The European Workshop on White Dwarfs was initiated by Prof. V. Weidemann, with the first meeting held in Kiel (FRG) in 1974. Since then a similar workshop has been held almost every two years: Frascati (1976), Tel Aviv (1978), Paris (1981), Kiel (1984), Frascati (1986) and Toulouse (1990). Two major IAU colloquia have also been devoted to the study of white dwarfs (No. 53, Rochester NY, 1979; No. 114, Hanover, NH, 1988). Our most recent meeting, the 8th Workshop, marks a number of important advances in both observational and theoretical studies of white dwarfs. This coincides with a significant expansion in the size of the community active in the field, as was clear from an increase in the number of participants between this workshop (77) and that in Toulouse (46), just two years ago. Key parts of any workshop are the discussion sessions following the pa pers. However, these are difficult to record and, very often, the 'live' flavour of the debates is lost. During this workshop we carried out an experiment, recording the discussion sessions on video tape and then transcribing these later for the proceedings. Although the recordings were made in non-studio conditions with regard to lighting and noise, only a very small part was unin telligible. All participants were given an opportunity to check their questions and answers for scientific accuracy and to correct any errors arising in the transcription process.
Download or read book Pulsating Stars written by Márcio Catelan and published by John Wiley & Sons. This book was released on 2014-12-29 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book surveys our understanding of stars which change in brightness because they pulsate. Pulsating variable stars are keys to distance scales inside and beyond the Milky Way galaxy. They test our understanding not only of stellar pulsation theory but also of stellar structure and evolution theory. Moreover, pulsating stars are important probes of the formation and evolution of our own and neighboring galaxies. Our understanding of pulsating stars has greatly increased in recent years as large-scale surveys of pulsating stars in the Milky Way and other Local Group galaxies have provided a wealth of new observations and as space-based instruments have studied particular pulsating stars in unprecedented detail.
Download or read book Unlocking the Secrets of White Dwarf Stars written by Hugh M. Van Horn and published by Springer. This book was released on 2014-11-14 with total page 335 pages. Available in PDF, EPUB and Kindle. Book excerpt: White dwarfs, each containing about as much mass as our Sun but packed into a volume about the size of Earth, are the endpoints of evolution for most stars. Thousands of these faint objects have now been discovered, though only a century ago only three were known. They are among the most common stars in the Milky Way Galaxy, and they have become important tools in understanding the universe. Yet a century ago only three white dwarfs were known. The existence of these stars completely baffled the scientists of the day, and solving the mysteries of these strange objects required revolutionary advances in science and technology, including the development of quantum physics, the construction and utilization of large telescopes, the invention of the digital computer, and the ability to make astronomical observations from space. This book tells the story of the growth in our understanding of white dwarf stars, set within the context of the relevant scientific and technological advances. Part popular science, part historical narrative, this book is authored by one of the astrophysicists who participated directly in uncovering some of the secrets of white dwarf stars.
Download or read book Nonradial Oscillations of Stars written by Wasaburō Unno and published by . This book was released on 1989 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Amplitude Modulation of Pulsation Modes in Delta Scuti Stars written by Dominic M. Bowman and published by Springer. This book was released on 2017-09-07 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: This outstanding thesis by Dominic Bowman provides a thorough investigation of long-standing questions as to whether amplitude modulation is astrophysical, whether it offers insights into pulsating stars, and whether simple beating of modes with stable amplitudes is unrecognised because of a lack of frequency resolution. In this thesis, the author studied a uniform sample of 983 delta Scuti stars—the most common type of main-sequence heat engine pulsator—that were observed nearly continuously for 4 years at stunning photometric precision of only a few parts per million by the Kepler space mission. With no mission planned to supersede the Kepler 4-year data set, this thesis will stand as the definitive study of these questions for many years. With revolutionary photometric data from the planet-hunting Kepler space mission, asteroseismic studies have been carried out on many hundreds of main-sequence solar-type stars and about 10,000 red giants. It is easy to understand why those stochastically driven stars have highly variable amplitudes. Over much of the rest of the Hertzsprung–Russell (HR) diagram, stellar pulsations are driven by heat mechanisms, which are much more regular than the stochastic driving in solar-like pulsators. Yet for decades, amplitude and frequency modulation of pulsation modes have been observed in almost all types of heat-driven pulsating stars. The author shows that the amplitude and frequency modulation are astrophysical, and he has investigated their implications and prospects to provide new insights into the delta Scuti stars and the many other types of heat-engine pulsators across the HR diagram.
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 Pulsating Stars written by Márcio Catelan and published by John Wiley & Sons. This book was released on 2015-02-02 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book surveys our understanding of stars which change in brightness because they pulsate. Pulsating variable stars are keys to distance scales inside and beyond the Milky Way galaxy. They test our understanding not only of stellar pulsation theory but also of stellar structure and evolution theory. Moreover, pulsating stars are important probes of the formation and evolution of our own and neighboring galaxies. Our understanding of pulsating stars has greatly increased in recent years as large-scale surveys of pulsating stars in the Milky Way and other Local Group galaxies have provided a wealth of new observations and as space-based instruments have studied particular pulsating stars in unprecedented detail.
Download or read book Stellar Remnants written by S.D. Kawaler and published by Springer Science & Business Media. This book was released on 2006-04-18 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: Three eminent scientists, each well known for the clarity of their writing, present for students and researchers what is known about the internal structure, origin and evolution of White Dwarfs, Neutron Stars and Black Holes, all objects at the final stage of stellar evolution. They cover fascinating topics such as pulsation of white dwarfs, millisecond pulsars or the dynamics around black holes. The book is written for graduate students in astrophysics, but is also of interest to professional astronomers and physicists.
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 Reports on Astronomy written by Richard M. West and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 717 pages. Available in PDF, EPUB and Kindle. Book excerpt: volume XIX A of IAU Transactions contains the reports by Presidents of Commissions, covering the period July 1981 - June 1984. The topics of IAU Commissions deal with all of contemporary astronomy and the present volume therefore constitutes an exhaustive and unique record of astronomical research during this interval. It is particularly useful for astronomers and other scientists who want to gain an overview of a certain field, not necessarily near their own research area. Each Commission President was requested, by early 1984, to begin prep arations for the compilation of his/her Commission report. All members of Commissions were asked to supply details about their individual research pro grammes. The ensuing, very substantial task of concatenating was undertaken in late 1984 by the Presidents, often supported by a team of authors, all recog nized authorities in their fields. In order to preserve some measure of uni formity - which is in any case very difficult with so many authors - editorial guidelines were sent to Presidents, including the number of pages allotted to each Commission.
Download or read book Stars as Laboratories for Fundamental Physics written by Georg G. Raffelt and published by University of Chicago Press. This book was released on 1996-05 with total page 692 pages. Available in PDF, EPUB and Kindle. Book excerpt: Much of what we know about neutrinos is revealed by astronomical observations, and the same applies to the axion, a conjectured new particle that is a favored candidate for the main component of the dark matter of the universe.
Download or read book Evaluation of Mode Identification Techniques in Two Key White Dwarf Pulsators written by Atsuko Nitta and published by . This book was released on 2000 with total page 414 pages. Available in PDF, EPUB and Kindle. Book excerpt: The success of asteroseismology lies in the correct identification of the normal modes of oscillation. The Whole Earth Telescope (WET) identified the normal modes of a helium white dwarf pulsator, GD358, by analyzing the period distribution of the pulsation modes. Another way to identify modes is by comparing pulsation amplitudes in the UV to the optical. To cross-calibrate the two mode identification methods, we observed GD358 in August, 1996 with the Hubble Space Telescope (HST) to obtain the UV data while observing nearly simultaneously from the ground. During our observations, GD358 went through a very drastic amplitude modulation in a time scale of hours. These short time scale amplitude changes made the direct UV to optical amplitude determinations difficult. We successfully eliminate the possibility that the 423s mode, the dominant mode at the time of these observations, is an l=3 or 4 g-mode pulsation, but we cannot unambiguously decide if it is an l=1 or 2. Theoretical calculations indicate that the massive pulsating DA white dwarf BPM 37093 has a crystallized interior (Winget et al. 1997; Kanaan 1996; Montgomery 1998). Crystallization was predicted theoretically 40 years ago (Kirshnitz 1960; Abrisokov 1961; Salpeter 1961) although uncertainties in the nature and extent of crystallization, as well as its associated effects, are the largest sources of uncertainty in calculating the ages of the coolest white dwarf stars- important chronometers of the galactic disk. The WET observed BPM 37093 in April 1998 and again in April 1999, simultaneously with the HST, in hopes of using both the period distribution and the amplitude comparison method to identify the l value of the modes and measure the first crystallized mass-fraction of a stellar interior. Here we also rule out the possibility of the observed modes being l=3 and higher and demonstrate that not all the observed modes are l-1. If all the observed modes are l-2, then we conclude that the crystallization mass fraction is between 0-80%, depending mainly on the surface H layer. In the end, we evaluate the amplitude comparison method and address advantages and problems using this method compared to other mode identification methods.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Literature 1989 Part 1 written by Astronomisches Rechen-Institut and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 1433 pages. Available in PDF, EPUB and Kindle. Book excerpt: From the reviews: "Astronomy and Astrophysics Abstracts has appeared in semi-annual volumes since 1969 and it has already become one of the fundemental publications in the fields of astronomy, astrophysics and neighbouring sciences. It is the most important English-language abstracting journal in the mentioned branches. ...The abstracts are classified under more than a hundred subject categories, thus permitting a quick survey of the whole extended material. The AAA is a valuable and important publication for all students and scientists working in the fields of astronomy and related sciences. As such it represents a necessary ingredient of any astronomical library all over the world." Space Science Review# "Dividing the whole field plus related subjects into 108 categories, each work is numbered and most are accompanied by brief abstracts. Fairly comprehensive cross-referencing links relevant papers to more than one category, and exhaustive author and subject indices are to be found at the back, making the catalogues easy to use. The series appears to be so complete in its coverage and always less than a year out of date that I shall certainly have to make a little more space on those shelves for future volumes." The Observatory Magazine#
Download or read book The Future of Asteroseismology written by Joyce Ann Guzik and published by Frontiers Media SA. This book was released on 2021-08-17 with total page 269 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Variable Stars as Essential Astrophysical Tools written by Cafer Ibanogammalu and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 838 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pulsating and eccentric binary stars play a fundamentally important role in deciphering the mass distribution within stars. The present volume reviews the fundamental concepts of both radial and nonradial oscillations in the stars, including the Sun. Helio- and astroseismological results are reviewed, from the basics to the most recent developments. A new theory is presented, which seems to explain the mechanism of the light and radial velocity variations of recently discovered Ap stars. This textbook covers almost all kinds of variable stars of widely different characteristics. It will serve as a reference text for a very long time to come, not only for specialists but also for undergraduate students of physics and astronomy.
