scholarly journals Radiative colliding winds models: the stagnation point singularity

1999 ◽  
Vol 193 ◽  
pp. 402-402
Author(s):  
Svetozar A. Zhekov ◽  
A. V. Myasnikov ◽  
N. A. Belov
Keyword(s):  
Steady State ◽  
Stagnation Point ◽  
Numerical Models ◽  
Mathematical Problem ◽  
Interaction Region ◽  
Stellar Winds ◽  
Point Singularity ◽  
X Ray ◽  
Colliding Winds ◽  
Radiative Interaction

The singularity at the stagnation point in steady-state colliding winds has a big influence on the structure of the radiative interaction region. None of the existing numerical models treats properly this mathematical problem. As a result, all the available models cannot be used for deriving the stellar winds parameters by making a comparison with the observed X-ray properties.

scholarly journals Optical and X-ray observations of stellar winds in Wolf-Rayet binaries

1995 ◽  
Vol 163 ◽  
pp. 262-270
Author(s):  
A. M. Cherepashchuk
Keyword(s):  
Chemical Composition ◽  
Core Temperature ◽  
Stellar Winds ◽  
Radial Expansion ◽  
Core Radius ◽  
X Ray ◽  
The Core ◽  
Basic Conclusion ◽  
Helium Stars ◽  
Colliding Winds

New spectrophotometric, photometric and polarimetric observations of V444 Cygni confirm the basic conclusion that the WN5 star has a small core radius (rc < 4 R⊙) and a high core temperature (Tc > 60 000 K), which are characteristic of massive helium stars. Values of rc < 3 — 6 R⊙ and Tc > 70 000 — 90 000 K for the core of the WN7 star in the Cygnus X-3 system agree well with this conclusion. A clumping structure of WR winds is suggested. X-ray observations of colliding winds in WR+O binaries suggest radial expansion and anomalous chemical composition of WR winds.

scholarly journals Colliding stellar winds: X-ray emission and instabilities

1995 ◽  
Vol 163 ◽  
pp. 486-494
Author(s):  
Ian R. Stevens
Keyword(s):  
Stellar Winds ◽  
Radiation Hydrodynamics ◽  
Hydrodynamic Simulations ◽  
X Ray ◽  
Radiation Fields ◽  
Basic Physics ◽  
Hydrodynamic Calculations ◽  
Basic Characteristics ◽  
Colliding Winds ◽  
Insight Into

Colliding stellar winds are an important part of early-type binaries. In this paper I discuss the phenomenon, concentrating mainly on the basic hydrodynamics of colliding winds, and the physics of X-ray emission. The following topics are covered:1) Basic physics: The basic characteristics of the shock-produced thermal X-ray emission, and discuss general trends of X-ray emission from colliding wind binaries (CWBs).2) Hydrodynamic simulations: Recent calculations have found that the interface in colliding winds is usually dynamically unstable, with three distinct instabilities.3) Gamma Velorum: recent ROSAT observations give much insight into colliding winds. I discuss recent hydrodynamic calculations pertaining to these observations.4) Radiation Hydrodynamics in CWBs: Recent calculations have included the effects of both radiation fields on the wind hydrodynamics in colliding wind systems.

scholarly journals Colliding stellar winds: recent advances in modelling

1999 ◽  
Vol 193 ◽  
pp. 289-297
Author(s):  
Ian R. Stevens ◽  
Julian M. Pittard
Keyword(s):  
Line Profile ◽  
Gas Dynamics ◽  
Interaction Region ◽  
Stellar Winds ◽  
Radiation Hydrodynamics ◽  
3D Simulations ◽  
X Ray ◽  
Recent Advances

We report on recent advances in the modelling of colliding stellar winds in WR binaries. Here, we concentrate on the modelling of X-ray observations using numerical gas-dynamics, in some cases including radiation hydrodynamics, and look in detail at a few systems, such as γ2 Velorum, η Carinae and HD 193793. We also report briefly on the modelling of infrared line-profile variability in a number of close WR+O-star systems, which can reveal further information on the dynamics of the interaction region. We discuss recent 3D-simulations and describe the exciting prospects that AXAF and XMM open up.

scholarly journals Colliding stellar winds: magnetic field structure in the interaction region

1999 ◽  
Vol 193 ◽  
pp. 400-401
Author(s):  
Svetozar A. Zhekov ◽  
A.V. Myasnikov ◽  
E.V. Barsky
Keyword(s):  
Magnetic Field ◽  
Rotational Velocity ◽  
Field Structure ◽  
Interaction Region ◽  
Stellar Winds ◽  
Magnetic Field Structure ◽  
Thermal Radio Emission ◽  
Colliding Winds ◽  
The Magnetic Field ◽  
Field Influence

The geometry structure of the magnetic field in colliding stellar winds is studied. It is shown that the magnetic field influence in the interaction region depends mainly on the ratio of the wind ram pressures of the components, the ratio of the stellar linear rotational velocity to the wind velocity of the magnetized star, and the stellar separation. For the radiative colliding winds the magnetic field influence increases with the importance of the radiative losses. An asymmetric magnetic field structure appears for a given set of binary parameters and the interaction region might be an asymmetric source of non-thermal radio emission.

scholarly journals X-rays from colliding winds in massive binaries

2016 ◽  
Vol 12 (S329) ◽  
pp. 359-360
Author(s):  
Yaël Nazé ◽  
Gregor Rauw
Keyword(s):  
High Resolution ◽  
Mass Loss ◽  
Strong Shock ◽  
Stellar Mass ◽  
Stellar Winds ◽  
X Rays ◽  
Current Generation ◽  
X Ray ◽  
Colliding Winds

AbstractIn a massive binary, the strong shock between the stellar winds may lead to the generation of bright X-ray emission. While this phenomenon was detected decades ago, the detailed study of this emission was only made possible by the current generation of X-ray observatories. Through dedicated monitoring and observations at high resolution, unprecedented information was revealed, putting strong constraints on the amount and structure of stellar mass-loss.

scholarly journals X-Ray Variability of the O Star ζ Puppis

1999 ◽  
Vol 169 ◽  
pp. 203-205
Author(s):  
Thomas W. Berghöfer
Keyword(s):  
Steady State ◽  
Numerical Simulations ◽  
Two Dimensions ◽  
Stellar Winds ◽  
Dynamical Processes ◽  
X Ray ◽  
Hot Gas ◽  
Wind Flows ◽  
Einstein Observatory

X-ray surveys carried out with the Einstein Observatory (Chlebowski et al. 1989) and ROSAT (Berghöfer et al. 1996) have shown that all O stars are soft X-ray emitters. Since O star winds are opaque at soft X-ray energies the stars or their photospheres cannot be the origin of the observed X-ray emission, thus, this emission must be produced in their stellar winds. Obviously, the X-ray emission is connected to dynamical processes present in the winds of O stars; steady-state computations for O star winds which are able to explain many of the observational features cannot predict any X-ray emission.Lucy & White (1980) suggested the presence of hot gas in the stellar winds which is produced in shocks developing from the growth of instabilities in the winds; supersonic wind flows in O stars are known to be intrinsically unstable. Numerical simulations confirmed this scenario. However, so far these simulations are limited to one or two dimensions and are not able to explain for instance the observed X-ray luminosity of O stars.

scholarly journals Hydrodynamics and high-energy physics of Wolf-Rayet colliding winds

1995 ◽  
Vol 163 ◽  
pp. 495-503 ◽  
Author(s):  
Vladimir V. Usov
Keyword(s):  
Particle Acceleration ◽  
High Energy Physics ◽  
High Energy ◽  
Stellar Winds ◽  
X Ray ◽  
And Shock Waves ◽  
Γ Ray ◽  
Ir Emission ◽  
Colliding Winds ◽  
Energy Physics

The stellar winds flowing out of the components of WR+OB binaries can collide and shock waves are formed. Stellar wind collision, particle acceleration by the shocks and generation of X-ray, γ-ray, radio and IR emission in WR+OB binaries are discussed.

scholarly journals NEAR-INFRARED AND X-RAY QUASI-PERIODIC OSCILLATIONS IN NUMERICAL MODELS OF Sgr A*

2012 ◽  
Vol 746 (1) ◽  
pp. L10 ◽  
Author(s):  
Joshua C. Dolence ◽  
Charles F. Gammie ◽  
Hotaka Shiokawa ◽  
Scott C. Noble
Keyword(s):  
Near Infrared ◽  
Numerical Models ◽  
Periodic Oscillations ◽  
X Ray ◽  
Sgr A

Measurement And Simulation Of X-Ray Emission From Multilayered Structures In Electron Probe Microanalysis.

1999 ◽  
Vol 5 (S2) ◽  
pp. 78-79
Author(s):  
C. Merlet ◽  
X. Llovet ◽  
F. Salvat
Keyword(s):  
Electron Probe ◽  
Numerical Models ◽  
Carbon Layer ◽  
Single Element ◽  
Surface Ionization ◽  
Copper Films ◽  
Multilayered Structures ◽  
X Ray ◽  
Electron Probe Microanalyzer ◽  
Quantitative Epma

Studies of x-ray emission from thin films on substrates using an electron probe microanalyzer (EPMA) provide useful information on the characteristics of x-ray generation by electron beams. In this study, EPMA measurements of multilayered samples were performed in order to test and improve analytical and numerical models used for quantitative EPMA. These models provide relatively accurate results for samples consisting of layers with similar average atomic numbers, because of their similar properties regarding electron transport and x-ray generation. On the contrary, these models find difficulties to describe the process when the various layers have very different atomic numbers. In a previous work, we studied the surface ionization of thin copper films of various thicknesses deposited on substrates with very different atomic numbers. In the present communication, the study is extended to the case of multilayered specimens.The studied specimens consisted of thin copper films deposited on a carbon layer which, in turn, was placed on a variety of single-element substrates, ranging from Be to Bi.

scholarly journals Aluminium Alloy Foam Modelling and Prediction of Elastic Properties Using X-ray Microcomputed Tomography

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 925
Author(s):  
Diogo Heitor ◽  
Isabel Duarte ◽  
João Dias-de-Oliveira
Keyword(s):  
Aluminium Alloy ◽  
Finite Element Modelling ◽  
Effective Properties ◽  
Numerical Models ◽  
Microcomputed Tomography ◽  
Cellular Materials ◽  
Metallic Foams ◽  
X Ray ◽  
The Impact ◽  
Structural Imperfections

X-ray microcomputed tomography has been gaining relevance in the field of cellular materials to characterize materials and analyse their microstructure. So, here, it was used together with finite element modelling to develop numerical models to estimate the effective properties (Young’s modulus) of aluminium alloy foams and evaluate the effects of processing on the results. A manual global thresholding technique using the mass as a quality indicator was used. The models were reconstructed (Marching Cubes 33), then simplified and analysed in terms of mass and shape maintenance (Hausdorff distance algorithm) and face quality. Two simplification procedures were evaluated, with and without small structural imperfections, to evaluate the impact of the procedures on the results. Results demonstrate that the developed procedures are good at minimizing changes in mass and shape of the geometries while providing good face quality, i.e., face aspect ratio. The models are also shown to be able to predict the effective properties of metallic foams in accordance with the findings of other researchers. In addition, the process of obtaining the models and the presence of small structural imperfections were shown to have a great impact on the results.

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