scholarly journals Atomic Data Needed for X-ray and EUV Astronomy

1992 ◽  
Vol 9 ◽  
pp. 573-574
Author(s):  
John C. Raymond
Keyword(s):  
Spectral Resolution ◽  
Atomic Data ◽  
Ionization State ◽  
Crystal Spectrometer ◽  
X Ray ◽  
Transmission Grating ◽  
Elemental Abundances ◽  
The Past ◽  
Accurate Temperature

AbstractThe astronomical X-ray and EUV satellites of the past generally had low enough spectral resolution that atomic data of modest quality was sufficient for most interpretation of the data. Typical proportional counter resolution Δ E/E ~ 1 permits a determination of the spectral shape sufficient for an estimate of the temperature of the emitting gas, but only the Fe K feature at 6.7 keV stands out as a distinct emission line. The higher spectral resolution Einstein Transmission Grating, Solid State Spectrometer, and Focal Plane Crystal Spectrometer instruments measured a score of emission lines or line blends, permitting determinations of the elemental abundances, temperature, and ionization state of the emitting gas. The higher spectral resolution and throughput of the BBXRT aboard the ASTRO mission and the instruments planned for EUVE, ASTRO-D, AXAF, and XMM will make possible a far more detailed analysis of the data. It should be possible to derive better abundances for more elements, accurate temperature distributions, electron densities, and accurate ionization states.

scholarly journals Atomic Data Needs for X-ray Astronomy

2002 ◽  
Vol 12 ◽  
pp. 82-83
Author(s):  
Nancy S. Brickhouse
Keyword(s):  
High Resolution ◽  
Atomic Data ◽  
Ionization Mechanism ◽  
Ionization State ◽  
Astrophysical Plasmas ◽  
X Ray ◽  
Physical Conditions ◽  
Elemental Abundances ◽  
The Status ◽  
Collisional Ionization

AbstractWith the launches of the Chandra X-ray Observatory and XMM-Newton, high resolution X-ray spectra of cosmic sources are broadening our understanding of the physical conditions, such as temperature, density, ionization state, and elemental abundances. X-ray emitting astrophysical plasmas can be generally classified by their dominant ionization mechanism, either collisional ionization or X-ray photoionization. The atomic data needs are significantly different for these two cases; however, for both cases it is important that we identify robust and accurate diagnostics and that we verify completeness of the broadband models. We discuss the status of the atomic data currently used in atomic databases for X-ray astronomy, in view of theoretical and experimental atomic physics considerations.

A Review of the Relative Merits of Low Powered WDXRF and EDXRF Spectrometers for Routine Quantitative Analysis

1990 ◽  
Vol 34 ◽  
pp. 193-199
Author(s):  
B. J. Price ◽  
J. Padur ◽  
N. S. Robson
Keyword(s):  
Quantitative Analysis ◽  
Energy Resolution ◽  
Spectral Resolution ◽  
X Ray ◽  
The Past

Historically, the development of XRF spectrometers has followed 2 main paths which are characterized by the means of spectral resolution they use. Those employing diffraction crystals and Braggs law to disperse the X-ray wavelengths are known as wavelength dispersive (WDX), whilst those usinq only the energy resolution of the detector, as enerqy dispersive (EDX). In the past these two have not normally been directly compared, because the WDX systems have always been the more expensive.

scholarly journals Massive Binaries

2007 ◽  
Vol 3 (S250) ◽  
pp. 119-132
Author(s):  
Anthony F. J. Moffat
Keyword(s):  
Massive Stars ◽  
Formation Processes ◽  
Subsequent Evolution ◽  
X Ray ◽  
Common Envelope ◽  
Blue Stragglers ◽  
The Past ◽  
Thermal Radio Emission ◽  
The Universe

AbstractAs with all binaries, those that contain massive stars reveal various degrees of interaction, depending mainly on orbital separation and age, although things happen much faster in massive binaries. Those massive binaries with initial periods exceeding ~10 years generally only interact via wind-wind collisions, with little or no effect on their subsequent evolution (unless located in dense clusters). Shorter-period systems show even stronger wind-wind collisions as a rule, but also interact more directly via Roche Lobe Overflow or Common Envelope, with dramatic effects on their evolution. If we didn't have binaries among massive stars, we would be missing a whole host of interesting phenomena in the Universe, such as sources of enhanced stellar X-ray or non-thermal radio emission, WR dust-spirals, inverse mass-ratios, very rapid spin, rejuvenation and massive blue-stragglers, enhanced cluster dynamics, many runaways and possibly even SMBHs and GRBs! On the other hand, non(or little)-interacting massive binaries are also useful to provide information on Star-Formation processes and determination of stellar parameters (such as the mass) that would otherwise be difficult or impossible to obtain from single stars. In this review, I highlight some of the developments that have occurred during the past few years since the last IAU Symposium on Massive Stars in 2002.

scholarly journals Binary Stucture of Accreting Neutron Stars

1998 ◽  
Vol 188 ◽  
pp. 105-106
Author(s):  
D.A. Leahy
Keyword(s):  
Neutron Stars ◽  
Spectral Resolution ◽  
Relevant Literature ◽  
Short Paper ◽  
X Rays ◽  
X Ray ◽  
The Past ◽  
Great Progress ◽  
Satellite Missions ◽  
X Ray Binaries

The study of X-ray binaries has made great progress with the advent in the past few years of a number of very capable X-ray astronomy missions. These are reviewed, for example, by Bradt et al 1992, and a set of recent relevant papers in Makino and Mitsuda, 1997. For example, ASCA has allowed a significant increase in sensitivity and spectral resolution in 0.5-10 keV X-rays (Tanaka et al 1994). Many recent Compton/GRO results on X-ray binaries are reviewed in the proceedings of the Second Compton Symposium (Fichtel et al 1994). Another source of recent results from analysis of data from several satellite missions is the proceedings of the Evolution of X-ray Binaries (Holt & Day, 1994). In this short paper, the emphasis is on guiding the reader to some relevant literature.

Chemical State Analysis using a Gearless Two-Crystal X-Ray Spectrometer

1991 ◽  
Vol 35 (A) ◽  
pp. 393-399
Author(s):  
Tokuzo Konishi ◽  
Kazuo Nishihagi ◽  
Kazuo Taniguchi
Keyword(s):  
High Resolution ◽  
Systematic Study ◽  
Chemical State ◽  
Crystal Spectrometer ◽  
X Ray ◽  
Analyzer Crystal ◽  
Chemical Effects ◽  
Scanning Range ◽  
State Analysis

A two-crystal spectrometer for chemical state analysis by high-resolution x-ray fluorescence spectrometry employs hall-screw and slide mechanisms rather than gears to obtain a 2θ scanning range of 40° -147°; a Δ2θ scanning step of 10−4 deg under vacuus; a 2θ resolution of 10−4 deg in determination of an intercrystal angle with encoder-based measurement; and servomechanical control of position. The spectrometer, although simple in structure, is a powerful instrument for chemical state analysis, as demonstrated by its high resolution, precision, and stability; as demonstrated in the determination of the Kα1 lines of first transition metals with Si(220) as analyzer crystal, and in its application to a systematic study of the chemical effects on Ni Kα1 and Kα2.

Neutron structures of ammonium tetrafluoroberyllate

1999 ◽  
Vol 55 (1) ◽  
pp. 17-23 ◽  
Author(s):  
R. C. Srivastava ◽  
W. T. Klooster ◽  
T. F. Koetzle
Keyword(s):  
Hydrogen Bonding ◽  
Ferroelectric Phase ◽  
Paraelectric Phase ◽  
Accurate Determination ◽  
Mirror Plane ◽  
Accurate Information ◽  
X Ray ◽  
The Past ◽  
Hydrogen Bonding Interactions

It is thought that hydrogen bonding is responsible for the ferroelectricity in ammonium tetrafluoroberyllate, (NH_{4})_{2}BeF_{4}. In the past X-ray data have been collected, but these did not permit accurate determination of the H-atom positions. In order to obtain more accurate information the neutron structures have now been determined for the paraelectric and ferroelectric phases. Going from the paraelectric to the ferroelectric phase, both the BeF_4^{2-} and the NH_4^+ ions rotate and shift from the mirror planes of the paraelectric phase. This results in removal of the mirror-plane symmetry and formation of a superlattice with the a axis doubled. Along the polar c axis, the NH_4^+ ions move towards the BeF_4^{2-} ions within chains of molecules and the chains move slightly relative to one another. The rotations and translations give rise to stronger hydrogen-bonding interactions.

Revisiting RV Tauri stars: first ionization potential (FIP) effect

2019 ◽  
Vol 97 (11) ◽  
pp. 1210-1220
Author(s):  
G. Yolalan ◽  
T. Şahin
Keyword(s):  
Asymptotic Giant Branch ◽  
Equilibrium Analysis ◽  
Atomic Data ◽  
Alternative Mechanism ◽  
Asymptotic Giant Branch Stars ◽  
Echelle Spectrograph ◽  
Elemental Abundances ◽  
First Time ◽  
Giant Branch Stars

We have derived elemental abundances of eight RV Tauri-type post-asymptotic giant branch stars: AR Sgr, CE Vir, DY Aql, HP Lyr, SS Gem, SZ Mon, TT Oph, and UZ Oph. The abundance analysis of these luminous stars is based on the high-resolution (R ≈ 55 000) optical echelle spectra obtained with the 2.1 m Struve reflector telescope and the CCD-equipped Sandiford Cassegrain echelle spectrograph at the McDonald Observatory. Standard 1D local thermodynamic equilibrium analysis provides a fresh determination of the atmospheric parameters and elemental abundances for 17 species including C, Na, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Y, and Nd. Then, the computed up-to-date abundances are used to investigate FIP in the program stars, as seen in the Sun and sun-like stars. Also, we scrutinize their behavior for dust–gas separation as an alternative mechanism to the FIP. For the first time, we provide atomic line lists with up-to-date atomic data employed in the analysis for AR Sgr, HP Lyr, SZ Mon, TT Oph, and UZ Oph.

scholarly journals Investigation of laser-produced chlorine plasma radiation for non-monochromatic X-ray scattering experiments

2006 ◽  
Vol 24 (3) ◽  
pp. 335-345 ◽  
Author(s):  
M. SCHOLLMEIER ◽  
G. RODRÍGUEZ PRIETO ◽  
F.B. ROSMEJ ◽  
G. SCHAUMANN ◽  
A. BLAZEVIC ◽  
...  
Keyword(s):  
Spectral Resolution ◽  
Pyrolytic Graphite ◽  
Line Emission ◽  
Plasma Radiation ◽  
High Spectral Resolution ◽  
Crystal Spectrometer ◽  
X Ray ◽  
Dense Plasmas ◽  
X Ray Scattering ◽  
Ray Scattering

The chlorine Heαradiation of polyvinyl chloride (PVC) was investigated with respect to X-ray scattering experiments on dense plasmas. The X-ray source was a laser-produced plasma that was observed with a highly reflective highly oriented pyrolytic graphite (HOPG) crystal spectrometer as it is used in current x-ray scattering experiments on dense plasmas. The underlying dielectronic satellites of Heαcannot be resolved, therefore the plasma was observed at the same time with a focusing spectrometer with spatial resolution. To reconstruct the spectrum a simple model to calculate the spectral line emission based on dielectronic recombination and inner shell excitation of helium- and lithium-like ions was used. The analysis shows that chlorine dielectronic satellite emission is intense compared to Heαin laser-produced chlorine plasmas with a temperature of 300 eV in this wavelength range of Δλ = 0.07 Å (ΔE= 43 eV). The method proposed in this paper allows deducing experimentally the role of the underlying dielectronic satellites in the scatter spectrum measured with a HOPG crystal spectrometer. It is shown that the dielectronic satellites can be neglected when the scattering is measured with low spectral resolution in the non-collective regime. They are of major importance in the collective scatter regime where a high spectral resolution is necessary.

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