scholarly journals Overloaded and fractured stellar winds

2003 ◽  
Vol 212 ◽  
pp. 56-60 ◽  
Author(s):  
Achim Feldmeier ◽  
Lida M. Oskinova ◽  
Wolf-Rainer Hamann ◽  
Stanley P. Owocki
Keyword(s):  
Wind Speed ◽  
Line Profile ◽  
Propagation Speed ◽  
Stellar Winds ◽  
Line Profiles ◽  
X Ray ◽  
On Line

We discuss the connection between wind overloading and discrete absorption components in P-Cygni line profiles from O-type stars. Overloading can create horizontal plateaus in the radial wind speed that cause the extra absorption in the line profile. The upstream propagation speed of these velocity plateaus is analyzed. The second part of the paper deals with X-ray emission from O-type stars. X-ray line profiles observed with Chandra and XMM-Newton are often symmetric, contrary to what is expected for lines from a homogeneous wind. We discuss the influence on line symmetry of photon escape channels in a strongly clumped wind.

Flat Crystal X-Ray Optics

1957 ◽  
Vol 1 ◽  
pp. 193-206 ◽  
Author(s):  
William J. Campbell ◽  
Melvin Leon ◽  
John Thatcher
Keyword(s):  
Wave Length ◽  
Pulse Height ◽  
Line Profiles ◽  
Line Broadening ◽  
Crystal Surfaces ◽  
X Ray ◽  
Line Intensities ◽  
Long Wave ◽  
On Line ◽  
College Park

AbstractAn investigation was undertaken by the Bureau of Mines at College Park, Md., to determine the effect of various combinations of collimators, analyzing crystals and detectors on line intensities, line-to-backgrouhd ratios, and spectral resolution. The research showed that line broadening due to mosaic crystal surfaces was greatly reduced and line splitting from faults was eliminatedby the use of two fine collimators (0.005 inch, spacing, 4 inch length). Line intensities were reduced, but lineto- background ratios arid line profiles were substantially improved with double collimators. Pulse height discrimination resulted in marked improvement in the line-to-background ratio in the long-wave length region, 2 to 10 A, but was much less effective for shorter wave lengths.

Real-time microstructure of shock-compressed single crystals from X-ray diffraction line profiles

2011 ◽  
Vol 44 (3) ◽  
pp. 574-584 ◽  
Author(s):  
Stefan J. Turneaure ◽  
Y. M. Gupta
Keyword(s):  
Single Crystals ◽  
Real Time ◽  
Line Profile ◽  
Distribution Model ◽  
Line Profiles ◽  
X Ray Diffraction ◽  
Multiple Diffraction ◽  
Heterogeneous Distribution ◽  
X Ray ◽  
Experimental Geometry

Methods to obtain and analyze high-resolution real-time X-ray diffraction (XRD) measurements from shock-compressed single crystals are presented. Procedures for extracting microstructural information – the focus of this work – from XRD line profiles are described. To obtain quantitative results, careful consideration of the experimental geometry is needed, including the single-crystal nature of the sample and the removal of instrumental broadening. These issues are discussed in detail. Williamson–Hall (WH) and profile synthesis (PS) analysis procedures are presented. More accurate than WH, the PS procedure relies on a forward calculation in which a line profile is synthesized by convoluting the instrumental line profile with a line profile determined from a diffraction simulation. The diffraction simulation uses the actual experimental geometry and a model microstructure for the shocked crystal. The shocked-crystal microstructural parameters were determined by optimizing the match between the synthesized and measured line profiles. XRD measurements on an Al crystal, shocked along [100] to 7.1 GPa using plate-impact loading, are used to demonstrate the WH and PS analysis methods. In the present analysis, the microstructural line broadening arises because of a distribution of longitudinal elastic microstrains. The WH analysis resulted in FWHM longitudinal microstrain distributions of 0.22 and 0.38% for Lorentzian and Gaussian line shape assumptions, respectively. The optimal FWHM longitudinal microstrain for the PS method was 0.35% with a pseudo-Voigt distribution (40% Lorentzian–60% Gaussian). The line profile measurements and PS analysis presented in this work provide new insight into the heterogeneous distribution of elastic strains in crystals undergoing elastic–plastic deformation during shock compression. Such microstrain distribution measurements are complementary to continuum measurements, which represent averages of the heterogeneous strains or stresses. The PS analysis is a general method capable of incorporating microstructural models more complex than the microstrain distribution model used in this work. As a next step, the PS method will be applied to line profiles of multiple diffraction peaks to separate strain- and size-broadening effects in shocked crystals.

scholarly journals X-ray spectroscopy of massive stellar winds: previous and ongoing observations of the hot star ζ Pup

2018 ◽  
Vol 14 (S346) ◽  
pp. 88-92
Author(s):  
N. Miller ◽  
W. Waldron ◽  
J. Nichols ◽  
D. Huenemoerder ◽  
M. Dahmer ◽  
...  
Keyword(s):  
Emission Line ◽  
Line Profile ◽  
Stellar Wind ◽  
Galactic Evolution ◽  
Stellar Winds ◽  
Hot Stars ◽  
X Ray ◽  
Wind Structure ◽  
Important Impact ◽  
Emission Line Profile

AbstractThe stellar winds of hot stars have an important impact on both stellar and galactic evolution, yet their structure and internal processes are not fully understood in detail. One of the best nearby laboratories for studying such massive stellar winds is the O4I(n)fp star ζ Pup. After briefly discussing existing X-ray observations from Chandra and XMM, we present a simulation of X-ray emission line profile measurements for the upcoming 840 kilosecond Chandra HETGS observation. This simulation indicates that the increased S/N of this new observation will allow several major steps forward in the understanding of massive stellar winds. By measuring X-ray emission line strengths and profiles, we should be able to differentiate between various stellar wind models and map the entire wind structure in temperature and density. This legacy X-ray spectrum of ζ Pup will be a useful benchmark for future X-ray missions.

scholarly journals X-ray line profiles from structured stellar winds

2003 ◽  
Vol 212 ◽  
pp. 214-215
Author(s):  
Lidia M. Oskinova ◽  
Achim Feldmeier ◽  
Wolf-Rainer Hamann
Keyword(s):  
Emission Line ◽  
Thin Shells ◽  
Stellar Winds ◽  
X Rays ◽  
Line Profiles ◽  
X Ray ◽  
Absorbing Material

Absorbing material compressed in a number of thin shells is effectively less opaque for X-rays than smoothly distributed gas. The calculated X-ray emission-line profiles are red-shifted if the emission arises from the starward side of the shells.

scholarly journals Polarimetry of Close Binary Systems; Observations and Interpretations

1980 ◽  
Vol 88 ◽  
pp. 65-70
Author(s):  
Ian S. McLean
Keyword(s):  
Binary Systems ◽  
Stokes Parameters ◽  
Close Binary ◽  
Stellar Winds ◽  
Line Profiles ◽  
Orbital Inclination ◽  
X Ray ◽  
Close Binary Systems ◽  
A New Technique ◽  
X Ray Binaries

Polarization caused by scattering of starlight on gaseous extrastellar material in close binary systems is reviewed. A simple physical derivation is given to illustrate how in principle, variations synchronous with the orbital period of the Stokes parameters of the linear polarization can yield the orbital inclination and other parameters. High resolution multichannel spectropolarimetry across the emission line profiles of binaries is discussed as a new technique in studying the physics and kinematics of gaseous streams and stellar winds. The methods have application to a range of binary objects including systems like Algol and Beta Lyrae, X-ray binaries, Of and Wolf-Rayet binaries, VV Cephei stars and symbiotic stars. Some new observational results are presented.

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.

Practical Applications of X-Ray Line Profile Analysis

2017 ◽  
pp. 1094-1132
Author(s):  
Jenő Gubicza
Keyword(s):  
Crystallite Size ◽  
Twin Boundary ◽  
Line Profile ◽  
Profile Analysis ◽  
Vacancy Concentration ◽  
Direct Method ◽  
Line Profile Analysis ◽  
Line Profiles ◽  
X Ray ◽  
Practical Applications

In the previous chapters, the theory and the main methods of diffraction peak profile analysis were presented. Additionally, the specialties in the measurement and the evaluation of line profiles in the cases of thin films and single crystals were discussed. In this chapter, some practical considerations are given in order to facilitate the evaluation of peak profiles and the interpretation of the results obtained by this method. For instance, the procedures for instrumental correction are overviewed. Additionally, how the prevailing dislocation slip systems and twin boundary types in hexagonal polycrystals can be determined from line profiles is shown. Besides the dislocation density, the vacancy concentration can also be obtained by the combination of electrical resistivity, calorimetric, and line profile measurements. The crystallite size and the twin boundary frequency determined by X-ray peak profile analysis are compared with the values obtained by the direct method of transmission electron microscopy. Furthermore, the limits of line profile analysis in the determination of crystallite size and defect densities are given. Finally, short overviews on the results obtained by peak profile analysis for metals, ceramics, and polymers are presented.

Practical Applications of X-Ray Line Profile Analysis

2014 ◽  
pp. 271-318
Keyword(s):  
Crystallite Size ◽  
Twin Boundary ◽  
Line Profile ◽  
Profile Analysis ◽  
Vacancy Concentration ◽  
Direct Method ◽  
Line Profile Analysis ◽  
Line Profiles ◽  
X Ray ◽  
Practical Applications

In the previous chapters, the theory and the main methods of diffraction peak profile analysis were presented. Additionally, the specialties in the measurement and the evaluation of line profiles in the cases of thin films and single crystals were discussed. In this chapter, some practical considerations are given in order to facilitate the evaluation of peak profiles and the interpretation of the results obtained by this method. For instance, the procedures for instrumental correction are overviewed. Additionally, how the prevailing dislocation slip systems and twin boundary types in hexagonal polycrystals can be determined from line profiles is shown. Besides the dislocation density, the vacancy concentration can also be obtained by the combination of electrical resistivity, calorimetric, and line profile measurements. The crystallite size and the twin boundary frequency determined by X-ray peak profile analysis are compared with the values obtained by the direct method of transmission electron microscopy. Furthermore, the limits of line profile analysis in the determination of crystallite size and defect densities are given. Finally, short overviews on the results obtained by peak profile analysis for metals, ceramics, and polymers are presented.

Evaluation of Straight and Curved Braun Position-Sensitive Proportional Counters on a Huber-Guinier X-Ray Diffraction System

1983 ◽  
Vol 27 ◽  
pp. 261-266 ◽  
Author(s):  
R.A. Newman ◽  
P. Moore Kirchhoff ◽  
T.G. Fawcett
Keyword(s):  
Scintillation Counter ◽  
Line Profiles ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
Camera System ◽  
X Ray ◽  
Proportional Counters ◽  
On Line ◽  
Position Sensitive ◽  
Gas Chamber

AbstractThe interfacing of both straight and curved Braun Position- Sensitive Proportional Counters (PSPC's) to a high resolution Huber-Guinier camera system has been accomplished, resulting in a 10 to 100-fold decrease in data collection times when compared to conventional Guinier (film or scintillation counter) detector techniques.Various factors causing line broadening were evaluated for both PSPC Guinier systems. The depth of the PSPC gas chamber was found to Have the greatest influence on line profiles. An R0% increase in peak half-widths was observed for PSPC-Guinier data compared to our highest resolution Guinier film data, but still yielded significantly better resolution than conventional powder diffractometer data obtained in our laboratory.

Line Profile Analysis (LPA) Methods: Systematic Ranking of the Quality of their Basic Assumptions

2004 ◽  
Vol 443-444 ◽  
pp. 127-130
Author(s):  
Arnold C. Vermeulen ◽  
Rob Delhez
Keyword(s):  
Line Profile ◽  
Profile Analysis ◽  
Line Profile Analysis ◽  
Line Profiles ◽  
Qualitative Comparison ◽  
New Developments ◽  
X Ray ◽  
Basic Assumptions ◽  
Wide Range

All methods of analyzing the broadening of XRD line profiles have to take into account two basic effects: broadening by the instrument - including the X-ray spectrum - and the characteristics of broadening by size effects and by lattice defects - including their interaction. These effects are handled in practice by a wide range of auxiliary assumptions. In this paper these assumptions and their quality with respect to "appropriateness of purpose" are listed and compared. By systematic ranking of these assumptions in accordance with their quality, a 2-dimensional map can be constructed that visualizes the differences in the quality of the assumptions. This 2-dimensional map brings a new viewpoint to the various methods for line profile analysis, because it enables a qualitative comparison of the assumptions of existing methods and new developments.

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