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 X-ray Emission from Massive Stars at the Core of Very Young Clusters

2016 ◽  
Vol 12 (S329) ◽  
pp. 362-365
Author(s):  
Norbert S. Schulz
Keyword(s):  
Massive Stars ◽  
Stellar Winds ◽  
X Rays ◽  
Stellar Clusters ◽  
Orion Nebula ◽  
X Ray ◽  
The Core ◽  
Hot Plasma ◽  
Young Clusters ◽  
Massive Cluster

AbstractMost cores of very young stellar clusters contain one or more massive stars at various evolutionary stages. Observations of the Orion Nebula Cluster, Trumpler 37, NGC 2362, RCW38, NGC 3603 and many others provide the most comprehensive database to study stellar wind properties of these massive cluster stars in X-rays. In this presentation we review some of these observations and results and discuss them in the context of stellar winds and possible evolutionary implications. We argue that in very young clusters such as RCW38 and M17, shock heated remnants of a natal shell could serve as an alternate explanation to the colliding wind paradigm for the hot plasma components in the X-ray spectra.

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 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 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 Detection of the Nuclear Source in the Cygnus a Galaxy

1994 ◽  
Vol 159 ◽  
pp. 375-376
Author(s):  
D.E. Harris ◽  
R.A. Perley ◽  
C.L. Carilli
Keyword(s):  
Image Processing ◽  
Surface Brightness ◽  
Main Body ◽  
Core Radius ◽  
Gas Distribution ◽  
Model Surface ◽  
X Ray ◽  
The Core ◽  
Cygnus A ◽  
The Galaxy

From a ROSAT HRI observation of Cygnus A (42 ksec), we detect x-ray emission from the galaxy identified with the radio source. This was accomplished by subtracting a modified King model: (Surface brightness ∝ to [1+(r/a)2](0.5–3β)) in order to study residual features once the main body of emission from diffuse gas had been deleted. The central source was present for all acceptable values of the core radius, a, and exponent, β. Details of the image processing, an evaluation of emission from the radio hotspots, and a study of the effect of the radio lobes on the gas distribution will be presented elsewhere.

scholarly journals Hα imaging of X-ray sources in selected globular clusters with SOAR

2009 ◽  
Vol 5 (S266) ◽  
pp. 508-508
Author(s):  
Pawel Pietrukowicz
Keyword(s):  
Energy Source ◽  
Globular Clusters ◽  
Binary Systems ◽  
Critical Role ◽  
Cataclysmic Variables ◽  
The Other ◽  
Theoretical Studies ◽  
Core Radius ◽  
X Ray ◽  
The Core

AbstractI present results of a search for cataclysmic variables (CVs) and chromospherically active binaries (ABs) as counterparts to X-ray sources detected with Chandra in six Galactic globular clusters (GCs): M 4, M 28, M 30, M 71, M 80, and NGC 6752. Binary systems play a critical role in the evolution of GCs, serving as an internal energy source countering the tendency of GC cores to collapse. Theoretical studies predict dozens of CVs in the cores of some GCs (e.g., 130 for M 28, 40 for M 30). A number of such binaries are also expected outside the core radius. However, few CVs are known so far in GCs. Using the 4.1m SOAR telescope, I have found 25 stars with Hα excess in the observed clusters. Six are candidate CVs, five are candidate active binaries. The other 14 objects with Hα excess are probably foreground/background stars or extragalactic sources.

Nanoprobe analysis of core–rim structure of carbides in TiC–20 wt% Mo2C–20 wt% Ni cermet

1999 ◽  
Vol 14 (11) ◽  
pp. 4129-4131 ◽  
Author(s):  
T. Yamamoto ◽  
A. Jaroenworaluck ◽  
Y. Ikuhara ◽  
T. Sakuma
Keyword(s):  
Electron Microscope ◽  
Chemical Composition ◽  
Sintering Temperature ◽  
Miscibility Gap ◽  
X Ray ◽  
The Core ◽  
Transmission Electron ◽  
Hrtem Observation ◽  
Discrete Change ◽  
Nanoscale Level

In order to get detailed information of the core–rim interface of carbides in TiC–20 wt% Mo2C–20 wt% cermet, chemical analysis in the vicinity of the interface was carried out by energy dispersive x-ray spectroscopy equipped with a high-resolution transmission electron microscope (HRTEM) with a field-emission-type gun. It was found that the chemical composition discretely changed across the core–rim interface at a nanoscale level, whereas HRTEM observation revealed that the interface is highly coherent. The discrete change in molybdenum content at the interface may suggest the existence of a miscibility gap between TiC and MoC systems at the sintering temperature.

scholarly journals Accretion and outflow of gas in Markarian 509

2012 ◽  
Vol 8 (S290) ◽  
pp. 45-48
Author(s):  
Jelle Kaastra ◽  
Pierre-Olivier Petrucci ◽  
Massimo Cappi ◽  
Nahum Arav ◽  
Ehud Behar ◽  
...  
Keyword(s):  
Black Hole ◽  
Chemical Composition ◽  
Time Scales ◽  
Time Dependent ◽  
Central Black Hole ◽  
Solar Mass ◽  
X Ray ◽  
The Core ◽  
Upper Limits ◽  
Central Regions

AbstractA major uncertainty in models for photoionised outflows in AGN is the distance of the gas to the central black hole. We present the results of a massive multiwavelength monitoring campaign on the bright Seyfert 1 galaxy Mrk 509 to constrain the location of the outflow components dominating the soft X-ray band. Mrk 509 was monitored by XMM-Newton, Integral, Chandra, HST/COS and Swift in 2009. We have studied the response of the photoionised gas to the changes in the ionising flux produced by the central regions. We were able to put tight constraints on the variability of the absorbers from day to year time scales. This allowed us to develop a model for the time-dependent photoionisation in this source. We find that the more highly ionised gas producing most X-ray line opacity is at least 5 pc away from the core; upper limits to the distance of various absorbing components range between 20 pc up to a few kpc. The more lowly ionised gas producing most UV line opacity is at least 100 pc away from the nucleus. These results point to an origin of the dominant, slow (v<1000 km s−1) outflow components in the NLR or torus-region of Mrk 509. We find that while the kinetic luminosity of the outflow is small, the mass carried away is likely larger than the 0.5 Solar mass per year accreting onto the black hole. We also determined the chemical composition of the outflow as well as valuable constraints on the different emission regions. We find for instance that the resolved component of the Fe-K line originates from a region 40–1000 gravitational radii from the black hole, and that the soft excess is produced by Comptonisation in a warm (0.2–1 keV), optically thick (τ~ 10–20) corona near the inner part of the disk.

scholarly journals Investigations of Electron Properties of Carbon Nanotubes Decorated with Platinum Nanoparticles with Their Varying Fraction

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Anna Dobrzańska-Danikiewicz ◽  
Dariusz Łukowiec ◽  
Jerzy Kubacki
Keyword(s):  
Carbon Nanotubes ◽  
Chemical Composition ◽  
Platinum Nanoparticles ◽  
Photoelectron Spectroscopy ◽  
Qualitative And Quantitative Analysis ◽  
X Ray ◽  
Qualitative And Quantitative ◽  
The Core ◽  
Wide Range ◽  
Varying Mass

The paper presents the outcomes of investigations into electron properties and a qualitative and quantitative analysis of the chemical composition of unmodified carbon nanotubes with comparison to nanotubes decorated with platinum nanoparticles. The fabricated nanocomposite materials of the CNT-Pt type differed in a varying mass concentration of platinum nanoparticles (5, 10, and 20% of Pt). X-ray photoelectron spectroscopy (XPS) was employed to examine the structure and to analyse chemical composition. Survey spectra measurements within a wide range of the binding energy of 0–1400 eV were performed in the first phase of the investigations. The core lines of C1s carbon, Pt4f platinum, and O1s oxygen and a valence band were then measured. The chemical composition of the studied materials was determined based on the measured spectra of the core lines. The purpose of the investigations is to determine the effect of platinum nanoparticles on the structure and electron properties of the fabricated CNT-Pt nanocomposites.

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.

Sign in / Sign up

Export Citation Format

Share Document