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Author: L. Errico Publisher: Springer Science & Business Media ISBN: 9401119244 Category : Science Languages : en Pages : 444
Book Description
In the last few years great improvements in the study of stellar jets and bipolar outflows have been achieved, both observationally and theoretically. High resolution observations at various frequencies (radio, IR, optical and X-ray) of these features in different types of objects have shown a large variety of morphologies at all scales often revealing contrasting symmetries which do not allow straightforward kinematic interpretations valid for all cases. In particular, at present, it seems very difficult to give a statistical definition of what the "standard properties" of jets and bipolar outflows are. On the theoretical side, the identification of physical processes capable of producing the observed rich morphological variety of jets and bipolar outflows and supporting them over long lifetimes is still controversial. Furthermore several models are actively discussed in an attempt of reaching a complete understanding of the phenomenon. The workshop provided an unique opportunity for both observers and theoreticians to gather together and produce an updated and exhaustive picture of the field. In addition the meeting has been enriched by the presentation of some works on jets in external galaxies. This topic was focused on what people working on stellar jets could learn from colleagues working on extragalactic jets and vice versa. Invited papers were prepared with the aim of giving the state of the art about scientific subjects; contributed papers and some selected poster papers presented, on the contrary, very recent results in the various fields.
Author: L. Errico Publisher: Springer Science & Business Media ISBN: 9401119244 Category : Science Languages : en Pages : 444
Book Description
In the last few years great improvements in the study of stellar jets and bipolar outflows have been achieved, both observationally and theoretically. High resolution observations at various frequencies (radio, IR, optical and X-ray) of these features in different types of objects have shown a large variety of morphologies at all scales often revealing contrasting symmetries which do not allow straightforward kinematic interpretations valid for all cases. In particular, at present, it seems very difficult to give a statistical definition of what the "standard properties" of jets and bipolar outflows are. On the theoretical side, the identification of physical processes capable of producing the observed rich morphological variety of jets and bipolar outflows and supporting them over long lifetimes is still controversial. Furthermore several models are actively discussed in an attempt of reaching a complete understanding of the phenomenon. The workshop provided an unique opportunity for both observers and theoreticians to gather together and produce an updated and exhaustive picture of the field. In addition the meeting has been enriched by the presentation of some works on jets in external galaxies. This topic was focused on what people working on stellar jets could learn from colleagues working on extragalactic jets and vice versa. Invited papers were prepared with the aim of giving the state of the art about scientific subjects; contributed papers and some selected poster papers presented, on the contrary, very recent results in the various fields.
Author: Amadeu J. L. Fernandes Publisher: Springer Science & Business Media ISBN: 9781402016172 Category : Science Languages : en Pages : 288
Book Description
The ubiquity of jet phenomena in young stellar objects, active galactic nuclei, symbiotic stars, planetary nebulae and x-ray binaries has driven a broad literature on the astrophysics of collimated mass ejection. One of the fundamental open problems in star formation is the understanding of the physical mechanisms by which mass is ejected from the protostellar system and collimated into jets. Locally, jets will regulate the system's angular momentum and therefore its evolution during the first few million years. At large scale, jets inject momentum into the cloud thus affecting its star formation efficiency and evolution.Many recent advances over the last years in the star-formation research (both theory and observations) together with the increasing availability of computational resources, provided an excellent opportunity to organise a workshop. This volume presents the results of the workshop discussions on the jet phenomenon on different astrophysical scales and covers interdisciplinary areassuch as steady state winds, time-dependent winds/jets, jet energetics and jet/wind propagation.
Author: D. Burgarella Publisher: Cambridge University Press ISBN: 9780521442213 Category : Science Languages : en Pages : 332
Book Description
A collection of edited review articles presented at a workshop at the Space Telescope Science Institute which gathered astrophysicists from the fields of extragalactic and galactic/stellar jets.
Author: Gerhard Klare Publisher: Springer Science & Business Media ISBN: 3642762387 Category : Science Languages : en Pages : 378
Book Description
In order to bring the scientific events of the meetings of the Astronomische Gesellschaft (AG) to the attention of the worldwide astronomical community, an annual publication, Reviews in Modern Astronomy, was established. It is devoted exclusively to . the invited reviews, the Karl Schwarz schild lectures, and the high light contributions from leading scientists reporting on recent progress and scientific achievements at their respective institutes. This third volume continues the yearbook series of publications of the society. It comprises the complete set of contributions presented during the spring meeting of the AG at Berlin in March 1990, which was dedicated to the topic "Accretion and Winds". In addition four latecomers (two review and two highlight papers) delivered at the fall meeting at Graz, Austria in September 1989 close this volume. Heidelberg, September 1990 G: Klare Contents Some New Elements in Accretion Disk Theory By F. Meyer (With 5 Figures) . . . . . . . . . . . . . . . . . . . . . . . 1 Mass Transfer and Evolution in Close Binaries By A. R. King (With 4 Figures) . . . . . . . . . . . . . . . . . . . . . . . 14 Radiation Hydrodynamics of the Boundary Layer of Accretion Disks in Cataclysmic Variables By W. Kley (With 6 Figures) . . . . . . . . . . . . . . . . . . . . . . . . 21 Curious Observations of Cataclysmic Variables By F. V. Hessman (With 10 Figures) . . . . . . . . . . . . . . . . . . . 32 Accretion in AM Herculis Stars 44 By A. D. Schwope (With 12 Figures) X-ray Diagnostics of Accretion Disks By G. Hasinger (With 12 Figures) . . . . . . . . . . . . . . . . . . . . . 60 Accretion Phenomena at Neutron Stars By A. Rebetzky, H. Herold, U. Kraus, H. -P. Nollert, and H. Ruder (With 13 Figures) . . . . . . . . . . . . . . . . . . . . . .
Author: Kanaris Tsinganos Publisher: Springer Science & Business Media ISBN: 3642005764 Category : Science Languages : en Pages : 662
Book Description
It is over a quarter of a century since the discovery of out?ows from young stars. The intervening years have led to remarkable advances in our understanding of this phenomenon. Much of the progress can be attributed to advances in facilities and technologies, including not only larger telescopes but also improved instrument and detector performance. In addition protostellar out?ows have now been imaged from the ground and space at high spatial resolution, e. g. with HST, and at a wide - riety of wavelengths from X-rays to radio waves, revealing more and more about their physics. This veritable revolution in observation has been accompanied by an exponential growth in our ability to numerically simulate the launching and pro- gation of jets. Codes continue to improve: they now incorporate more physics and are increasingly ef?cient through, for example, techniques such as adaptive mesh re?nement and the use of parallel processing in cluster environments. Simulating the launching and propagation of a jet all the way from the vicinity of the star up to 4 several thousand AU (a size range of10 ) is now much closer. In more recent times, developments in observation, theory and numerical s- ulation have been joined by laboratory jet experiments reproducing, on centimetre scales, that which is seen in astrophysics to stretch for several parsecs.
Author: J. R. Jokipii Publisher: University of Arizona Press ISBN: 0816538638 Category : Science Languages : en Pages : 1048
Book Description
Until the advent of space physics, astrophysical plasmas could be studied only using ground-based observations. Although observational methods have advanced over recent decades, the merging of heliospheric physics with astrophysics is far from complete due to the vastly different techniques employed by astronomers and space physicists. That astrophysical plasmas can be studies directly is a major advance in astrophysical research. The solar wind from the Sun is only one of many examples of solar winds, but it provides scientists with a basis for understanding how these formerly disparate disciplines are related. Cosmic Winds and the Heliosphere is a comprehensive sourcebook on conceptually correlated topics in astrophysical winds and heliospheric physics. The contributors review the various kinds of winds, such as solar wind, winds of cataclysmic variables, and winds from pulsating stars. They then examine the physics of wind origin and physical phenomena in winds. including heliospheric shocks, magnetohydrodynamic turbulence, and kinetic phenomena. A final section considers interactions with surrounding media, with contributions ranging from studies of the interstellar cloud surrounding the solar system to considerations of solar wind interaction with comets. Prepared to the scrupulous standards of the University of Arizona Space Science Series, Cosmic Winds and the Heliosphere is an essential volume for astronomers and space physicists.
Author: Marc Christopher White Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Protostellar jets and winds play a crucial role in the dynamics and evolution of the star-formation process. They may effectively regulate mass accretion by removing angular momentum from the circumstellar disc. Despite their importance, the physical processes driving the outflow phenomena remain poorly understood. This thesis presents a consistent model for the outflow structure and dynamics of the young stellar object DG Tauri, using data of unprecedented spatial and spectral resolution from the Near-infrared Integral Field Spectrograph (NIFS) on Gemini North. The approaching outflow shows two components in [Fe II] 1.644 micron emission. A stationary recollimation shock is observed in the high-velocity jet, in agreement with previous X-ray and FUV observations. The pre-shock jet velocity, and inferred jet launch point (400-700 km/s and 0.02-0.07 AU, respectively), are significantly different from previous estimates. Jet 'acceleration' beyond the shock is interpreted as intrinsic velocity variability. Careful analysis reveals no evidence of jet rotation, contrary to previous work. A wide-angle, low-velocity blueshifted molecular outflow is observed in H2 1-0 S(1) 2.1218 micron emission. Both outflows are consistent with a magnetocentrifugal disc wind origin, although an X-wind origin for the jet cannot be excluded. The lower-velocity [Fe II] component surrounds the jet, and is interpreted as a turbulent mixing layer generated by lateral jet entrainment of molecular wind material. An analytical model of an entrainment layer is constructed, based on Riemann decomposition of directly observable outflow parameters. The model reproduces the velocity field of the entrained material without invoking an arbitrary 'entrainment efficiency' parameter. The luminosity and mass entrainment rate estimated using the model are in agreement with observations. Such lateral entrainment requires a magnetic field strength of order a few mG at hundreds of AU above the disc surface; independent arguments are advanced to support this conclusion. The receding outflow of DG Tau takes on a bubble-shaped morphology. Kinetic models indicate this structure is a quasi-static bubble with an internal velocity field describing expansion. It is proposed that this bubble forms because the receding counterjet from DG Tau is obstructed by a clumpy ambient medium. There is evidence of interaction between the counterjet and ambient material, which is attributed to the large molecular envelope around the DG Tau system. An analytical model of a momentum-driven bubble is shown to be consistent with observations. It is concluded that the bipolar outflow from DG Tau is intrinsically symmetric; the observed asymmetries are due to environmental effects. The observational interpretations and comprehensive modelling of the DG Tau outflows presented in this thesis constitute a significant step forward in gaining a full physical understanding of how stars accrete their mass. The complex nature of the approaching jet provides the first clear indications of the diverse phenomena associated with protostellar mass loss. The different morphology of the receding outflow has highlighted the role of environmental factors in defining outflow characteristics. Together this work presents a new and more detailed view of the complex mechanisms associated with the formation of a low-mass star.
Author: Edvige Corbelli Publisher: Springer Science & Business Media ISBN: 1402034075 Category : Science Languages : en Pages : 551
Book Description
Theideatocelebrate50yearsoftheSalpeterIMFoccurredduringtherecent IAU General Assembly in Sydney, Australia. Indeed, it was from Australia that in July 1954 Ed Salpeter submitted his famous paper "The Luminosity Function and Stellar Evolution" with the rst derivation of the empirical stellar IMF. This contribution was to become one of the most famous astrophysics papers of the last 50 years. Here, Ed Salpeter introduced the terms "original mass function" and "original luminosity function", and estimated the pro- bility for the creation of stars of given mass at a particular time, now known as the "Salpeter Initial Mass Function", or IMF. The paper was written at the Australian National University in Canberra on leave of absence from Cornell University (USA) and was published in 1955 as 7 page note in the Astroph- ical Journal Vol. 121, page 161. To celabrate the 50th anniversary of the IMF, along with Ed Salpeter’s 80th birthday, we have organized a special meeting that brought together scientists involved in the empirical determination of this fundamental quantity in a va- ety of astrophysical contexts and other scientists fascinated by the deep imp- cations of the IMF on star formation theories, on the physical conditions of the gas before and after star formation, and on galactic evolution and cosmology. The meeting took place in one of the most beautiful spots of the Tuscan countryside, far from the noise and haste of everyday life.
Author: L. Errico
Author: L. Errico
Author: Amadeu J. L. Fernandes
Author: D. Burgarella
Author: Gerhard Klare
Author: Kanaris Tsinganos
Author: J. R. Jokipii
Author: Marc Christopher White
Author: Edvige Corbelli
Author: C. E. Normand
Author: Seung-Urn Choe