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 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 The central cluster and X-ray emission from Sgr A*

2006 ◽  
Vol 2 (S238) ◽  
pp. 347-348
Author(s):  
Robert F. Coker ◽  
Julian M. Pittard
Keyword(s):  
Black Hole ◽  
Stellar Winds ◽  
Solar Mass ◽  
Hydrodynamic Simulations ◽  
X Ray ◽  
Central Cluster ◽  
The Galaxy ◽  
Early Type Stars ◽  
Sgr A ◽  
Hydrodynamic Data

AbstractAt the centre of the Milky Way is Sgr A*, a putative 3 million solar mass black hole with an observed luminosity that is orders of magnitude smaller than that expected from simple accretion theories. The number density of early-type stars is quite high near Sgr A*, so the ensemble of their stellar winds has a significant impact on the black hole's environment.We present results of 3D hydrodynamic simulations of the accretion of stellar winds onto Sgr A*. Using the LANL/SAIC code, RAGE, we model the central arc-second of the Galaxy, including the central cluster stars (the S-stars) with orbits and wind parameters that match observations. A significant fraction of the winds from the S stars becomes gravitationally bound to the black hole and thus could provide enough hot gas to produce the X-ray emission seen by Chandra. We perform radiative transfer calculations on the 3D hydrodynamic data cubes and present the resulting synthetic X-ray spectrum.

scholarly journals 3D hydrodynamic simulations of colliding winds in V444 Cygni

1999 ◽  
Vol 193 ◽  
pp. 386-387 ◽  
Author(s):  
Julian M. Pittard ◽  
Ian R. Stevens
Keyword(s):  
3D Model ◽  
Hydrodynamic Simulations ◽  
X Ray ◽  
Recent Developments ◽  
Colliding Winds

We report on recent developments in simulating colliding wind X-ray emission, and present a 3D model of the WR binary V444 Cyg (WN5+O6) which self-consistently includes radiative driving.

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 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 Accretion of stellar winds in high-mass X-ray binaries

2012 ◽  
Vol 8 (S290) ◽  
pp. 219-220 ◽  
Author(s):  
Petr Hadrava ◽  
Jan Čechura
Keyword(s):  
Numerical Model ◽  
Accretion Rate ◽  
Circumstellar Matter ◽  
High Mass ◽  
Stellar Winds ◽  
Radiation Hydrodynamics ◽  
X Ray ◽  
Compact Component ◽  
Balmer Lines ◽  
X Ray Binaries

AbstractOur analysis of optical spectroscopy of high-mass X-ray binaries like Cyg X-1 confirms that most of the Balmer-lines emission anticorrelated with the X-ray flux originates from the circumstellar matter between the donor star and the accreting compact component. In order to study its structure and variability and the consequent accretion rate we have developed a 3-D numerical model based on radiation hydrodynamics of the supergiant stellar wind. The results show a non-stationary BHL-accretion on the compact component.

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 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.

Quantitative Analysis Of X-Ray Images From Geological Materials

1990 ◽  
Vol 48 (2) ◽  
pp. 244-245
Author(s):  
J. M. Paque ◽  
R. Browning ◽  
P. L. King ◽  
P. Pianetta
Keyword(s):  
Quantitative Analysis ◽  
Bulk Composition ◽  
Principal Component ◽  
Analytical Description ◽  
Bulk Sample ◽  
Geological Samples ◽  
X Ray ◽  
Software And Hardware ◽  
And Storage ◽  
Insight Into

Geological samples typically contain many minerals (phases) with multiple element compositions. A complete analytical description should give the number of phases present, the volume occupied by each phase in the bulk sample, the average and range of composition of each phase, and the bulk composition of the sample. A practical approach to providing such a complete description is from quantitative analysis of multi-elemental x-ray images.With the advances in recent years in the speed and storage capabilities of laboratory computers, large quantities of data can be efficiently manipulated. Commercial software and hardware presently available allow simultaneous collection of multiple x-ray images from a sample (up to 16 for the Kevex Delta system). Thus, high resolution x-ray images of the majority of the detectable elements in a sample can be collected. The use of statistical techniques, including principal component analysis (PCA), can provide insight into mineral phase composition and the distribution of minerals within a sample.

Copper–oxygen Dynamics in Tyrosinase

2019 ◽  
Author(s):  
Nobutaka Fujieda ◽  
Sachiko Yanagisawa ◽  
Minoru Kubo ◽  
Genji Kurisu ◽  
Shinobu Itoh
Keyword(s):  
Catalytic Mechanism ◽  
Substrate Binding ◽  
Active Form ◽  
Copper Ion ◽  
Atomic Resolution ◽  
Oxygen Species ◽  
X Ray ◽  
Oxygen Dynamics ◽  
Insight Into ◽  
Copper Centre

To unveil the activation of dioxygen on the copper centre (Cu<sub>2</sub>O<sub>2</sub>core) of tyrosinase, we performed X-ray crystallograpy with active-form tyrosinase at near atomic resolution. This study provided a novel insight into the catalytic mechanism of the tyrosinase, including the rearrangement of copper-oxygen species as well as the intramolecular migration of copper ion induced by substrate-binding.<br>

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