Studies Of The Circumstellar Environments Of Late Type Stars
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| Author | : Kevin Marvel |
| Publisher | : Universal-Publishers |
| Total Pages | : 526 |
| Release | : 1996-12 |
| Genre | : Nature |
| ISBN | : 1581120613 |
The dissertation presents the results of a multi-epoch very long baseline interferometric study of water masers located in the extended atmospheres of evolved stars. The research was performed using the Very Long Baseline Array and Very Large Array of the National Radio Astronomy Observatory. Optical monitoring of the stars was provided by the American Association of Variable Star Observers, the Variable Star Network and Dr. Bill Neely of the NF/Observatory. Water masers of found to exist in a region where a population inversion of the rotation transition of 22 GHz can be maintained by collisional pumping. The masers are identified as individual pockets of gas, which have the good velocity coherence and may be imaged using radio interferometry. Stellar winds are initiated in these sources by dust formation and acceleration of the gas through momentum coupling. The typical wind speeds in the region of the water masers are 10 to 20 km/s The water masers are followed through several epochs of observation and exhibit proper motions consistent with the assumed source distance and the measured outflow of velocity in the water maser region. Estimates of the distance to the sources using statistical approximation are in agreement with the currently accepted distances to the stars. A detailed kinematic model is used to describe the flow motions of the gas in the maser region. The regions are found to be complex and not well modeled by uniform radial outflow, radial outflow with rotation, or radial with acceleration. The reasons for this are explored and include anisotropic velocity fields induced through non-uniform dust formations near the star and incomplete sampling of the outflow due to a lack of detected masers. Possibilities for future work in the subject are described and include more sophisticated modeling, more sensitive observations, and analysis of other maser species.
| Author | : Francesco Paresce |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 414 |
| Release | : 2013-06-29 |
| Genre | : Science |
| ISBN | : 354069398X |
It has always been ESO's aim to operate the VLT in an interferometric mode (VLTI) which allows the coherent combination of stellar light beams col lected by the four 8-m telescopes and by several smaller auxiliary telescopes. In December 1993, in response to financial difficulties, the ESO Council de cided to postpone implement at ion of the VLTI, Coude trains and associated adaptive optics for all the UTs but included provisions for continuing tech nological and development programmes devoted to the aim of reintroducing these capabilities at the earliest possible date. The desirability of carrying out the full VLTI programme as originally envisaged at the earliest possible moment has not, however, diminished, es pecially in view of VLTI's exceptional capabilities and resulting potential for new and exciting discoveries. In recent years, interferometric projects have begun to playa central role in ground-based high-resolution astronomy, and numerous instruments have been completed or are in the process of construc tion. Several large-aperture interferometers will probably co me on-line near the turn of the century. The impending presence of these new instruments represents an important incentive both for clarifying the scientific cases for various VLTI implementation plans and for ensuring VLTI's competitiveness in the international context over the next 1O~20 years.
| Author | : International Astronomical Union. Symposium |
| Publisher | : Cambridge University Press |
| Total Pages | : 564 |
| Release | : 2008-02-14 |
| Genre | : Nature |
| ISBN | : 9780521874649 |
Astrophysical masers, naturally occurring microwave and radio-wave emissions, provide an important tool to investigate astrophysical environments. Several thousand maser sources have been observed in the interstellar medium and star formation regions, in the expanding winds from evolved stars, in the compressed shells of supernovae remnants, in comets and in the centers of galaxies. Masers are also useful for studying the structure and dynamics of our own galaxy, while masers in other galaxies are now used for cosmological studies and studies of galactic nuclei. This volume contains the latest research on the topic as presented at IAU Symposium 242, only the third international symposium on astrophysical masers. Over 125 astronomers from 18 different countries gathered in Alice Spring, Australia, for discussions on maser research.
| Author | : Richard O. Gray |
| Publisher | : Princeton University Press |
| Total Pages | : 611 |
| Release | : 2021-06-08 |
| Genre | : Science |
| ISBN | : 1400833361 |
Written by leading experts in the field, Stellar Spectral Classification is the only book to comprehensively discuss both the foundations and most up-to-date techniques of MK and other spectral classification systems. Definitive and encyclopedic, the book introduces the astrophysics of spectroscopy, reviews the entire field of stellar astronomy, and shows how the well-tested methods of spectral classification are a powerful discovery tool for graduate students and researchers working in astronomy and astrophysics. The book begins with a historical survey, followed by chapters discussing the entire range of stellar phenomena, from brown dwarfs to supernovae. The authors account for advances in the field, including the addition of the L and T dwarf classes; the revision of the carbon star, Wolf-Rayet, and white dwarf classification schemes; and the application of neural nets to spectral classification. Copious figures illustrate the morphology of stellar spectra, and the book incorporates recent discoveries from earth-based and satellite data. Many examples of spectra are given in the red, ultraviolet, and infrared regions, as well as in the traditional blue-violet optical region, all of which are useful for researchers identifying stellar and galactic spectra. This essential reference includes a glossary, handy appendixes and tables, an index, and a Web-based resource of spectra. In addition to the authors, the contributors are Adam J. Burgasser, Margaret M. Hanson, J. Davy Kirkpatrick, and Nolan R. Walborn.
| Author | : D.C.B Whittet |
| Publisher | : CRC Press |
| Total Pages | : 405 |
| Release | : 2018-10-08 |
| Genre | : Science |
| ISBN | : 1482268647 |
Dust is a ubiquitous feature of the cosmos, impinging directly or indirectly on most fields of modern astronomy and astrophysics. Dust in the Galactic Environment, Second Edition provides a thorough overview of the subject, covering general concepts, methods of investigation, important results and their significance, relevant literature, and some suggestions for promising avenues of future research. Since the publication of the first edition of this popular graduate text, major advances have been made in our understanding of astrophysical dust, especially in the light of exciting new results from space- and ground-based telescopes, together with advances in laboratory astrophysics and theoretical modeling. This new, expanded edition highlights the latest results and provides a context for future research opportunities. The first chapter provides a historical perspective for current research and an overview of interstellar environments and the role of dust in astrophysical processes, followed by a discussion of the cosmic history of the chemical elements expected to be present in dust and an examination of the effect of gas-dust interactions on gas phase abundances. The next several chapters describe the observed properties of interstellar grains, such as their extinction, polarization, absorption, and emission characteristics. Then, the book explores the origin and evolution of dust, tracing its life cycle in a succession of environments from circumstellar shells to diffuse interstellar clouds, molecular clouds, protostars, and protoplanetary disks. The final chapter summarizes progress toward a unified model. Dust in other galaxies is discussed as an integral part of the text rather than as a distinct topic requiring separate chapters. Containing extensive references and problems to aid understanding and illustrate basic principles, the book is ideally suited for graduate and advanced undergraduate courses. It will also be an invaluable reference for postgraduate students and researchers working in this important field.
| Author | : Hans-Peter Gail |
| Publisher | : Cambridge University Press |
| Total Pages | : 699 |
| Release | : 2014 |
| Genre | : Science |
| ISBN | : 0521833795 |
This book explores why dust forms around stars, and how to model stellar dust formation and dust-forming environments consistently.
| Author | : Graeme D. Watt |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 608 |
| Release | : 2012-12-06 |
| Genre | : Science |
| ISBN | : 9401101477 |
The conference recorded in this volume was one of the events organised to celebrate the centenary of the (re)establishment of the Royal Observatory, Edinburgh, on Blackford Hill in 1884. Circumstellar Matter was selected as the topic because of important contributions toward research in the field by recent observations in the infrared and submillimetre, particularly with the two telescopes which the Observatory has both operated and built instru mentation for - the United Kingdom Infrared Telescope (UKIRT) and the James Clerk Maxwell Telescope (JCMT). The programme aimed to cover as many aspects of circumstellar matter as could fit into a one-week meeting, omitting only planetary nebulae, which had been well served by meetings in the previous two years. We thank the international scientific advisory com mittee (overleaf) for their help in selecting the Invited Reviewers around which the programme was built. The Invited Reviews and oral contributions are included in the order and sections in which they were presented, even where re-ordering might have been more logical. We did not attempt to categorise the poster contributions but have included them in alphabetical order. An evening session for viewing and discussing posters in an unhurried atmosphere was very successful. A competition for the best poster was held and the prize was awarded for that by Lindqvist, Lucas, Olofsson, Omont, Eriksson & Gustafsson.
| Author | : |
| Publisher | : |
| Total Pages | : 402 |
| Release | : |
| Genre | : Environmental geology |
| ISBN | : |
| Author | : |
| Publisher | : |
| Total Pages | : 892 |
| Release | : 1994 |
| Genre | : Aeronautics |
| ISBN | : |
| Author | : Andrea Richichi |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 583 |
| Release | : 2007-10-12 |
| Genre | : Science |
| ISBN | : 3540742565 |
Celebrating the completion of the first phase of VLTI development, the ESO workshop The Power of Optical/IR Interferometry, held in 2005, gathered researchers together to review and discuss not just interferometers, but also how science uses interferometers and their impact on astronomy as a whole. This volume contains the proceedings of this workshop, serving as a reference for astronomers working with optical and infrared interferometry.
