Download or read book Hydrogen deficient Central Stars of Planetary Nebulae written by Helge Todt and published by . This book was released on 2009 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Hydrogen deficient Stars written by Klaus Werner and published by . This book was released on 2008 with total page 424 pages. Available in PDF, EPUB and Kindle. Book excerpt: "These are the proceedings of a conference on Hydrogen-Deficient Stars held at the University of Tübingen, Germany, from September 17-21 2007. This conference was the third in a series of international colloquia on this topic. The first one took place in Mysore, India in 1985, and the second one a decade alter, 1995 in Bamberg, Germany. Twelve years later it was considered useful to gather again to discuss the progress and the future directions in this field. At the conference 68 participants from 20 countries presented 25 invited talks, 27 contributed talks, and 16 posters. Hydrogen-deficiency is exhibited by many evolved high-and low-mass stars. Therefore research on hydrogen-deficient stars is quite diverse since such stars are found in almost every region of the Hertzsprung-Russell diagram. The stellar classes discussed in detail at the conference were: R Coronae Borealis stars, extreme helium stars, Wolf-Rayet central stars of planetary nebulae, PG 1159 stars and related objects, white dwarfs of spectral type DO, DB, and DQ, and helium-rich subdwarf O and B stars. Also highlighted were hydrogen-deficient stars in close binary systems (AM Cvn and ultracompact low-mass X-ray binaries), massive Wolf-Rayet Stars and their relation to Type I supernovae and Gamma-ray bursts. The different classes of objects discussed in this volume are grouped by spectral and pulsational characteristics, by evolutionary scenarios such as late helium flashes and double-degenerate mergers, and by links among the classes."--Publisher's website.
Download or read book On the Origin and Evolution of Wolf Rayet Central Stars of Planetary Nebulae written by Kyle David DePew and published by . This book was released on 2011 with total page 227 pages. Available in PDF, EPUB and Kindle. Book excerpt: The origin of hydrogen-deficiency in the central stars of planetary nebulae (CSPNe) is currently a topic of heated debate. This class of objects is comprised of Wolf-Rayet ([WR]) stars, weak emission-line stars (WELS), and PG 1159 stars, each differentiated by a set of unique spectral characteristics. For some time, there have been questions surrounding the evolutionary status of these rare stars: what environmental conditions, such as chemical abundances, are necessary for their emergence, whether any of them represent different stages of development in the same class of stars, and what the characteristics of their progenitors may be. However, such investigations have been hampered by a lack of a sufficient number of these stars and their various sub-classes until recently. This thesis presents the significant discovery of 22 new [WR] stars and 10 new WELS, many uncovered specifically during this thesis in the course of the MASH survey and through serendipitous fibre placement during follow-up of MASH objects. All examples have been carefully classified as accurately as possible using the best current available data though for many this remains a preliminary assignment pending deeper spectra. This work expands the known sample of H-deficient stars by 30%, allowing a more detailed study of their properties than previously possible and moving us closer to a more complete census of local H-deficient CSPNe. In the course of our classifications, Abell 48 was found to be a particularly interesting object. Further analysis of nebular chemical abundances, modeled temperature, and ionization state as indicated by the chemical species present suggests that the CSPN of Abell 48 may be very similar to the CSPN of PB 8, which has recently been redesignated as the founding member of a new and rare [WN/WC] class (Todt et al. 2010). Its similarity to and differences with other oxygen-rich [WO] and carbon-rich [WC] stars as well as previously identified [WN] stars are examined. All these stars have also been studied in the context of a new subclass-dynamical age relationship that we have also discovered. This major finding is the first to show evidence of an evolutionary trend amongst the [WR] population and was made possible by use of the powerful new surface brightness-radius (SB-r) relation of Frew (2008) that can, at last, provide accurate distances to PN (and hence also their central stars). Key data acquired here as well as modeled effective temperatures and excitation classes of other [WR]s, WELS and PG 1159 central stars found in the literature were also utilized in generating this relationship. Finally, continuing with the SB-r relation, the scale heights of the most complete available sample of [WR], WELS and PG 1159 CS populations are determined and compared. These data show that both WELS and PG 1159 stars are found to possess significantly higher Galactic heights than the members of the [WR] class, implying that PG 1159s do not all descend from [WR]s, and that WELS are not evolutionarily related to [WR]s. This is another major finding of this work. It is possible, however, that the WELS class, and perhaps the PG 1159 class as well, are heterogeneous groups.
Download or read book Hydrogen Deficient Stars written by C. Simon Jeffery and published by . This book was released on 1996 with total page 530 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Hydrogen Deficient Stars and Related Objects written by K. Hunger and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first helium star was discovered in 1942, the first scientific meeting on the subject, however, took place in 1985. The meeting was hence long overdue for, in the meantime, a substantial amount of material had been accumulated by a rather small, but active scientific community. Hence, it appeared necessary to review the field in order to define the subject, assess its present status and discuss future developments. Hydrogen deficiency is a widespread phenomenon, occurring in a large variety of stellar and nonstellar objects. It can be readily detected in B stars as these exhibit both hydrogen and helium lines, if the elements are present in appreciable amounts. It becomes less manifest in cool stars, where the temperature is too low to excite helium and where one has to devise indirect methods for proving hydrogen deficiency. Clearly, it was not possible to discuss the whole complex of hydrogen deficiency, i.e. in both stars and diffuse matter, but rather to concentrate on the issue of helium stars.
Download or read book Hydrogen Deficient Central Stars of Planetray Nebulae written by Helge Todt and published by . This book was released on 2009 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Importance of Binaries in the Formation and Evolution of Planetary Nebulae written by Henri M. J. Boffin and published by Springer Nature. This book was released on 2019-09-04 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: It is now clear that a binary evolutionary pathway is responsible for a significant fraction of all planetary nebulae, with some authors even going so far as to claim that binarity may be a near requirement for the formation of an observable nebula. This has led to the requirement that textbooks most likely need to be rewritten. Building upon the review of Jones and Boffin in Nature Astronomy (2017), this Springer Brief takes a first step in this direction. It offers the first expanded presentation of all the theoretical and observational support for the importance of binarity in the formation of planetary nebulae, initially focusing on common envelope evolution but also covering wider binaries. This book emphasises the wider impact of the field, highlighting the critical role binary central stars of planetary nebulae have in understanding a plethora of astrophysical phenomena, including type Ia supernovae, chemically peculiar stars and circumbinary exoplanets.
Download or read book An Introduction to Planetary Nebulae written by Jason J. Nishiyama and published by Morgan & Claypool Publishers. This book was released on 2018-05-25 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book we will look at what planetary nebulae are, where they come from and where they go. We will discuss what mechanisms cause these beautiful markers of stellar demise as well as what causes them to form their variety of shapes. How we measure various aspects of planetary nebulae such as what they are made of will also be explored. Though we will give some aspects of planetary nebulae mathematical treatment, the main points should be accessible to people with only a limited background in mathematics. A short glossary of some of the more arcane astronomical terms is at the end of the book to help in understanding. Included at the end of each chapter is an extensive bibliography to the peer reviewed research on these objects and I would encourage the reader interested in an even deeper understanding to read these articles.
Download or read book Planetary Nebulae written by Harm J. Habing and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 543 pages. Available in PDF, EPUB and Kindle. Book excerpt: Planetary nebulae present a fascinating range of shapes and morphologies. They are ideal laboratories for the study of different astrophysical processes: atomic physics, radiative transfer, stellar winds, shocks, wind-wind interaction, and the interaction between stellar winds and the interstellar medium. In addition, planetary nebulae provide information about the late stages of stellar evolution. In the last five years studies of planetary nebulae have progressed very rapidly and new phenomena and insights have been gained. This is partly due to new observations (e.g. from the Hubble Space Telescope, the ISO satellite and new infrared and millimeter spectrographs) and partly to the advancement of hydrodynamic simulations of the structures of planetary nebulae (PN). Many of these new results were reported at IAU Symposium 180 in Groningen, the Netherlands, on August 26 to 30, 1996. This symposium was dedicated to one of the pioneers of PN research: Stuart Pottasch. These proceedings contain chapters on: Introduction to PN with the basic parameters Distances of PN The central stars of PN The envelopes of PN The evolution from AGB to PN The evolution from PN to white dwarfs PN in the galactic context PN in extragalactic systems The future of PN research . The book contains 29 reviews and more than 200 shorter contributions.
Download or read book Wolf Rayet Stars Observations Physics Evolution written by C. de Loore and published by Springer Science & Business Media. This book was released on 1982-07-31 with total page 648 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of IAU Symposium No. 99, held at Cozumel, Mexico, September 18-22, 1981
Download or read book Planetary Nebulae written by Grigor Aramovich Gurzadi︠a︡n and published by . This book was released on 1969 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Planetary Nebulae written by Stuart R. Pottasch and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 335 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this book is to give a detailed description of the planetary nebulae including the relevant astronomical observations and their interpretation. Considerable attention is given to the evolution of these objects as well as to their physical characteristics. I t is hoped that the book be useful to both advanced research workers and to students with some background in astronomy. In this regard, the book should serve as a text as well as a reference work. The many tables included are expected to be useful for both purposes. The references are generally not included in the text except for historical purposes in an effort to improve readability. References are given at the end of each chapter together with sufficient text to describe their content. No attempt has been made to make the list of references complete; on the contrary it has generally been limited to the most recent literature on the subject which in turn refers to earlier research. Again, exceptions have been made for references of historical interest.
Download or read book Asymmetric Planetary Nebulae VII written by Quentin A. Parker and published by MDPI. This book was released on 2019-03-21 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains the best and most up-to-date contributions in the field of late stage stellar evolution, as presented at the APNVII conference in Hong Kong in December 2017. A total of 60 scientists from 20 countries gathered to present, listen, interact and discuss the most current issues and problems in planetary nebulae and related objects research. The emphasis of this influential series of meetings, which was the seventh occasion over the last 20 years, has always been on the hypothesized and observed physical shaping mechanisms of the ejected nebulae that have such wonderful and intriguing forms. This special Galaxies conference issue of fully refereed contributions brings together a representative compilation of the meeting presentations in paper form. It captures the current “snap shot” status of this research field in some real sense. Such proceedings are well received and can be used as a reference material by both participants and all others working in the field for years to come.
Download or read book Planetary Nebulae in Our Galaxy and Beyond IAU S234 written by International Astronomical Union. Symposium and published by Cambridge University Press. This book was released on 2006 with total page 606 pages. Available in PDF, EPUB and Kindle. Book excerpt: Planetary nebulae represent the brief transition between Asymptotic Giant Branch stars and White Dwarfs. As multi-wavelength laboratories they have played a key role in developing our understanding of atomic, molecular, dust and plasma processes in astrophysical environments. The means by which their wonderfully diverse morphologies are obtained is currently the subject of intense research, including hydrodynamical shaping mechanisms and the role of binarity, stellar magnetic fields and rotation. Their contribution to the chemical enrichment of galaxies is another very active research area, as is the ever growing use of their narrow high luminosity emission lines to probe the dynamics and mass distributions of galaxies and the intergalactic media of clusters of galaxies. IAU S234 summarises the current status of research on the properties and processes of planetary nebulae, as reported in reviews and papers by leading experts working in the field.
Download or read book Planetary Nebulae written by R. Weinberger and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 633 pages. Available in PDF, EPUB and Kindle. Book excerpt: Planetary nebulae are a keystone for the understanding of the evolution of stars, for deep insights into the physical processes prevailing in highly excited dilute nebulae, and for the chemical evolution in galaxies. These objects, displaying an intriguing morphology, have a `short' lifetime of a few tens of thousands of years, and have become one of the best studied classes of celestial sources. However, despite large and successful efforts from both the observational and theoretical side, planetary nebulae still keep some of their secrets (like the widely unknown distances) and will undoubtedly also be objects of thorough investigations in the years to come.
Download or read book Central Stars of Planetary Nebulae Showing O Or Of type Spectra written by Sara Ridgway Heap and published by . This book was released on 1970 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Physics and Dynamics of Planetary Nebulae written by Grigor A. Gurzadyan and published by Springer Science & Business Media. This book was released on 2013-04-09 with total page 518 pages. Available in PDF, EPUB and Kindle. Book excerpt: Planetary nebulae are the classic subject of astrophysics. The physical pro cesses occurring in this highly ionized gaseous medium, the formation of emis sion lines in clearly specified conditions, the continuous emission extending from the far ultraviolet up to infrared and radio frequencies, the generation of exotic forms of radiation predicted by atomic physics, along with methods for deciphering the observed spectra and detecting physical and kinematic parameters of the radiating medium, etc. - all these problems form the solid foundations of the physical theory of gaseous nebulae. They are an essential part of the arsenal of powerful tools and concepts without which one cannot imagine understanding and interpreting the enormous diversity of processes taking place in the Universe - in gaseous envelopes surrounding the stars of various classes, from cool dwarfs and flare stars up to hot supergiants, as well as in stellar chromospheres and coronae, in atmospheres of unstable and anomalous stars, in circumstellar clouds and gaseous shells born in nova and supernova explosions, in diffuse nebulae and the interstellar medium, in interacting binary systems, in galaxies with emission lines, in quasars, etc. The last thirty years have seen a turning-point in our knowledge concern ing the very nature of planetary nebulae (PNs). The radio emission of PNs was discovered after it was predicted theoretically. On the other hand, the powerful infrared emission discovered both in the continuum and in emission lines was never expected.
