scholarly journals Astrophysical Plasmas and Atomic Processes

1998 ◽  
Vol 188 ◽  
pp. 43-46 ◽  
Author(s):  
J.S. Kaastra
Keyword(s):  
Atomic Processes ◽  
Astrophysical Plasmas ◽  
X Ray ◽  
Ionization Balance ◽  
Smith Model ◽  
Non Equilibrium

Several plasma codes are available for the analysis of hot astrophysical plasmas. Among the oldest are the Raymond-Smith model (Raymond & Smith 1977) and Mewe-Gronenschild model (Mewe et al. 1985, 1986). Minor updates to this last code have resulted in the meka model (Kaastra 1992); major updates (most importantly the ionization balance and the treatment of the Fe-L complex) resulted in the mekal code (Mewe, Kaastra & Liedahl 1995). Here also the plasma codes of Masai (1984) and Landini & Monsignori Fossi (1990) should be mentioned. The RS, meka and mekal codes are included in the XSPEC fitting package, the latest mekal code is incorporated in the SPEX package (Kaastra et al. 1996). Both Masai's code and SPEX contain non-equilibrium ionization (NEI) modes. All these codes differ in details, see Brickhouse et al. (1995) for an overview. Most important for the analysis of X-ray data is the ionization balance that is used for iron and the treatment of the Fe-L complex.

scholarly journals Atomic processes in optically thin plasmas

2015 ◽  
Vol 11 (A29A) ◽  
pp. 291-294
Author(s):  
Jelle S. Kaastra ◽  
Liyi Gu ◽  
Junjie Mao ◽  
Missagh Mehdipour ◽  
Ton Raassen ◽  
...  
Keyword(s):  
Black Holes ◽  
Charge Transfer ◽  
Accurate Data ◽  
Atomic Processes ◽  
Physical Processes ◽  
Astrophysical Plasmas ◽  
X Ray ◽  
Recent Developments ◽  
The Universe ◽  
Atomic Parameters

AbstractThe Universe contains a broad range of plasmas with quite different properties depending on distinct physical processes. In this contribution we give an overview of recent developments in modeling such plasmas with a focus on X-ray emission and absorption. Despite the fact that such plasmas have been investigated already for decades, and that overall there is a good understanding of the basic processes, there are still areas, where improvements have to be made that are important for the analysis of astrophysical plasmas. We present recent work on the update of atomic parameters in the codes that describe the emission from collisional plasmas, where older approximations are being replaced now by more accurate data. Further we discuss the development of models for photo-ionised plasmas in the context of outflows around supermassive black holes and models for charge transfer that are needed for analyzing the data from the upcoming ASTRO-H satellite.

scholarly journals Emission Lines From Hot Astrophysical Plasmas

1990 ◽  
Vol 115 ◽  
pp. 1-10 ◽  
Author(s):  
John C. Raymond
Keyword(s):  
Spectral Lines ◽  
Emission Lines ◽  
Physical Parameters ◽  
Relative Importance ◽  
Astrophysical Plasmas ◽  
X Ray ◽  
Elemental Abundances ◽  
Computer Codes ◽  
Measurement Uncertainties ◽  
Ionization Balance

AbstractThe spectral lines which dominate the X-ray emission of hot, optically thin astrophysical plasmas reflect the elemental abundances, temperature distribution, and other physical parameters of the emitting gas. The accuracy and level of detail with which these parameters can be inferred are limited by the measurement uncertainties and uncertainties in atomic rates used to compute the model spectrum. This paper discusses the relative importance and the likely uncertainties in the various atomic rates and the likely uncertainties in the overall ionization balance and spectral line emissivities predicted by the computer codes currently used to fit X-ray spectral data.

scholarly journals NON-EQUILIBRIUM MODELING OF THE FE XVII 3C/3D LINE RATIO IN AN INTENSE X-RAY FREE-ELECTRON LASER EXCITED PLASMA

2015 ◽  
Vol 801 (1) ◽  
pp. L13 ◽  
Author(s):  
S. D. Loch ◽  
C. P. Ballance ◽  
Y. Li ◽  
M. Fogle ◽  
C. J. Fontes
Keyword(s):  
Free Electron ◽  
Free Electron Laser ◽  
Line Ratio ◽  
Equilibrium Modeling ◽  
X Ray ◽  
Non Equilibrium

scholarly journals What Do We Really Know About the Winds of Massive Stars?

2007 ◽  
Vol 3 (S250) ◽  
pp. 89-96
Author(s):  
D. John Hillier
Keyword(s):  
Mass Loss ◽  
Massive Stars ◽  
Standard Theory ◽  
Stellar Winds ◽  
X Rays ◽  
X Ray ◽  
Stellar Photosphere ◽  
Weak Winds ◽  
Ionization Balance ◽  
Loss Rates

AbstractThe standard theory of radiation driven winds has provided a useful framework to understand stellar winds arising from massive stars (O stars, Wolf-Rayet stars, and luminous blue variables). However, with new diagnostics, and advances in spectral modeling, deficiencies in our understanding of stellar winds have been thrust to the forefront of our research efforts. Spectroscopic observations and analyses have shown the importance of inhomogeneities in stellar winds, and revealed that there are fundamental discrepancies between predicted and theoretical mass-loss rates. For late O stars, spectroscopic analyses derive mass-loss rates significantly lower than predicted. For all O stars, observed X-ray fluxes are difficult to reproduce using standard shock theory, while observed X-ray profiles indicate lower mass-loss rates, the potential importance of porosity effects, and an origin surprisingly close to the stellar photosphere. In O stars with weak winds, X-rays play a crucial role in determining the ionization balance, and must be taken into account.

scholarly journals Infrared Analysis of Supernova Remnants

1988 ◽  
Vol 101 ◽  
pp. 363-378 ◽  
Author(s):  
Eli Dwek
Keyword(s):  
Supernova Remnants ◽  
Infrared Emission ◽  
Infrared Analysis ◽  
Atomic Processes ◽  
Infrared Observations ◽  
X Ray ◽  
Physical Conditions ◽  
The Galaxy ◽  
Dust Grain ◽  
Astronomical Satellite

AbstractInfrared observations of supernova remnants obtained with the Infrared Astronomical Satellite provide new insights into the dynamics and energetics of the remnants, and into their interaction with the ambient interstellar medium. In most remnants the infrared emission arises from dust that is collisionally heated by the X-ray emitting gas. The infrared observations can therefore be used as a diagnostic for the physical conditions of the shocked gas. In particular, it is shown that all the prominent X-ray remnants in the Galaxy and in the LMC cool mainly by dust grain collisions instead of atomic processes.

scholarly journals Non-Equilibrium Ionization in Puppis A

1983 ◽  
Vol 101 ◽  
pp. 245-252
Author(s):  
P. F. Winkler ◽  
C. R. Canizares ◽  
B. C. Bromley
Keyword(s):  
High Resolution ◽  
Spectroscopic Data ◽  
Supernova Remnant ◽  
Optical Data ◽  
Equilibrium Conditions ◽  
X Ray ◽  
Flux Measurements ◽  
Far From Equilibrium ◽  
Einstein Observatory ◽  
Non Equilibrium

High resolution X-ray spectroscopy of the brightest knot of emission in the Puppis A supernova remnant shows that it is made up of ionizing plasma, far from equilibrium. Flux measurements in several X-ray lines enable us to determine the non-equilibrium conditions: electron temperature, ion populations, and time since the knot was heated by the supernova shock. Imaging and spectroscopic data from the Einstein Observatory together suggest that this knot is a cloud of density about 10 cm−3 which has recently been shocked to a temperature 7 × 106 K. Radio and optical data on the region appear consistent with this picture.

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