X-ray Spectral Lines Research Articles

PREDICTIONS FOR THE REVERBERATING SPECTRAL LINE FROM A NEWLY FORMED BLACK HOLE ACCRETION DISK: CASE OF TIDAL DISRUPTION FLARES

Tidal Disruption Events (TDEs) can be perfect probes of dormant SMBHs in normal galaxies. During the rising phase, the accretion luminosity can increase by orders of magnitude in several weeks and the emergent ionizing radiation illuminates the fresh accretion flow. In this paper, we simulated the evolution of the expected spectral line profile of iron due to such a flare by using a ray-tracing code with effects of general relativity (GR) taken into account. We found that the time-dependent profile changes significantly with black hole spin, inclination angle with respect to the black-hole equatorial plane, and the expansion velocity of the ionization front. At low values of spin, a "loop" feature appears in the line profile vs. time plot when the inclination is no less than $30^\circ$ and the expansion velocity $v_{\rm exp}$ is no less than half speed of light, due to a shadow in the emission of the truncated disk. In the light curve two peaks occur depending on the inclination angle. At large $v_{\rm exp}$, a shallow "nose" feature may develop ahead of the loop, its duration depends on the expansion velocity and the inclination angle. We explore the entire interval of black hole spin parameter ranging from extreme prograde to extreme retrograde rotation, $-1<a<1$. In the prograde case, a low-energy tail appears to be more pronounced in the evolving centroid energy of the line. Our results demonstrate the importance to search for X-ray spectral lines in the early phase of TDE flares in order to constrain black hole mass and spin, as well as properties of the innermost accretion flow.

Determination of the thickness of polycrystalline thin films by using X-ray methods

The knowledge of the thickness of thin layer on substrate is quite important, sometimes even critical, for analysis of the layer properties and behavior. Among a large number of methods the X–ray methods are non-destructive and can simultaneously provide information about the structure and microstructure of the layer. These methods are capable to resolve the thickness of the layer within the range 5–300nm for in-house diffractometers. The method of the first choice is usually the X-ray reflectivity. In the case of reflection of X-rays the most limiting factor is the roughness of the interfaces, i.e. the layer and substrate and the thickness inhomogeneity. If the roughness increases certain value the intensity of the specularly reflected intensity drops down very suddenly and the thickness of the layer couldn't be decided. In that case one can use X-ray powder diffraction in very asymmetric geometry, for example in the coplanar grazing-exit parallel beam setup. In this setup the thickness of the layer can be determined from attenuation of the integrated intensity by decreasing the angle of exit of the diffracted rays. Another X-ray based method is the X-ray fluorescence spectrometry where the layer thickness is determined by analyzing the X-ray spectral lines from the layer/substrate. In our contribution we will demonstrate how to use the mentioned methods in order to determine the thickness of the thin layer on the example of TiO2 thin polycrystalline films.

AN EXTREME GRAVITATIONALLY REDSHIFTED IRON LINE AT 4.8 KeV IN Mrk 876

X-ray spectral lines at unforeseen energies are important because they can shed light on the extreme physical conditions of the environment around the supermassive black holes of active galactic nuclei (AGN). Mrk 876 displays such a line at 4.8 keV rest-frame energy. A possible interpretation of its origin can be found in the hotspot scenario. In this scenario the primary radiation from a flare in the hot corona of an AGN illuminates a limited portion of the accretion disk that emits by fluorescence. In this context the line can represent an extreme gravitationally redshifted Fe line originating on the accretion disk below 6 gravitational radii from a rotating supermassive black hole. The correct estimate of the line significance requires a dedicated approach. Based on an existing rigorous approach, we have performed extensive Monte Carlo simulations. We determine that the line is a real feature at ~99 confidence level.

Effect of Opacity on Solar Coronal Soft X-Ray Oxygen VIII Spectral Line

To study the effect of opacity on the solar x-ray spectral line, using the method of escape factor, we analyze the effect of opacity on the solar oxygen VIII spectral line, and we estimate the effective emission thickness of the oxygen VIII emitting region in the solar atmosphere. Results show that the opacity has a greater effect on the solar oxygen VIII spectral line, and the effective emission thickness of the oxygen VIII ion is greater than that for some ions in the solar ultraviolet spectral line. This study has important reference significance in solar plasma diagnoses in the x-ray region.

Measuring the x-ray resolving power of bent potassium acid phthalate diffraction crystals.

This report presents the results from measuring the X-ray resolving power of a curved potassium acid phthalate (KAP(001)) spectrometer crystal using two independent methods. It is part of a continuing effort to measure the fundamental diffraction properties of bent crystals that are used to study various characteristics of high temperature plasmas. Bent crystals like KAP(001) do not usually have the same diffraction properties as corresponding flat crystals. Models that do exist to calculate the effect of bending the crystal on the diffraction properties have simplifying assumptions and their accuracy limits have not been adequately determined. The type of crystals that we measured is being used in a spectrometer on the Z machine at Sandia National Laboratories in Albuquerque, New Mexico. The first technique for measuring the crystal resolving power measures the X-ray spectral line width of the characteristic lines from several metal anodes. The second method uses a diode X-ray source and a double crystal diffractometer arrangement to measure the reflectivity curve of the KAP(001) crystal. The width of that curve is inversely proportional to the crystal resolving power. The measurement results are analyzed and discussed.

Measurement of high-energy (10-60 keV) x-ray spectral line widths with eV accuracy.

A high resolution crystal spectrometer utilizing a crystal in transmission geometry has been developed and experimentally optimized to measure the widths of emission lines in the 10-60 keV energy range with eV accuracy. The spectrometer achieves high spectral resolution by utilizing crystal planes with small lattice spacings (down to 2d = 0.099 nm), a large crystal bending radius and Rowland circle diameter (965 mm), and an image plate detector with high spatial resolution (60 μm in the case of the Fuji TR image plate). High resolution W L-shell and K-shell laboratory test spectra in the 10-60 keV range and Ho K-shell spectra near 47 keV recorded at the LLNL Titan laser facility are presented. The Ho K-shell spectra are the highest resolution hard x-ray spectra recorded from a solid target irradiated by a high-intensity laser.

Wavelength-dispersive X-ray Fluorescence Spectrometric Determination of Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in Komatiites

Abstract Komatiites are mantle-derived ultramafic volcanic rocks. Komatiites have been discovered in several States of India, notably in Karnataka. Studies on the distribution of trace-elements in the komatiites of India are very few. This paper proposes a simple, accurate, precise, rapid, and non-destructive wavelength-dispersive x-ray fluorescence (WDXRF) spectrometric technique for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in komatiites, and discusses the accuracy, precision, limits of detection, x-ray spectral–line interferences, inter-element effects, speed, advantages, and limitations of the technique. The accuracy of the technique is excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Zr, Nb, Ba, Pb, and Th and very good (within 4%) for Y. The precision is also excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th. The limits of detection are: 1 ppm for Sc and V; 2 ppm for Cr, Co, and Ni; 3 ppm for Cu, Zn, Rb, and Sr; 4 ppm for Y and Zr; 6 ppm for Nb; 10 ppm for Ba; 13 ppm for Pb; and 14 ppm for Th. The time taken for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in a batch of 24 samples of komatiites, for a replication of four analyses per sample, by one operator, using a manual WDXRF spectrometer, is only 60 hours.

X-ray Spectral Line Shape Analysis of Asphalt Binders

An X-ray diffraction (XRD) technique has been applied to the study of asphalt binders. XRD patterns were obtained using a Rigaku DMax 2200 V-PC (personal computer). Jade software (version 6.1) was used to perform the peak search, full width at half-maximum, and profile fits with Pearson VII and pseudo-Voigt mathematical functions over the areas of interest. The XRD spectra were also modeled in Mathematica using a generalized Fermi function (GFF). Analysis shows a mixed correlation in the data in terms of mathematical fit, analysis of fit, and plotting. Aromaticity and crystallite size parameters were calculated for the asphalt binders using the data from the three functions (Pearson VII, pseudo-Voigt, GFF). Results are compared and discussed with respect to aging effects, asphalt binder models (Yen, Yen–Mullins), and fuel technology.

Effects of the self-absorption of X-ray spectral lines in the presence of the laser-cluster interaction

The effects of self-absorption of X-ray spectral lines have been experimentally observed in the plasma of cluster targets. It has been shown that, since a cluster target is condensed in the femtosecond time scale and gaseous in the picosecond time scale, self-absorption effects can observed for X-ray spectral lines that are predominantly emitted during the action of a laser pre-pulse. The self-absorption effects are manifested as spectral lines with asymmetric profiles where the long-wavelength wing is suppressed compared to the short-wavelength wing. The observation of asymmetric contours is important for the diagnostics of the laser-cluster interaction because it enables the conclusion of whether the laser pre-pulse completely destroys the cluster and makes it possible to quantitatively estimate the size of the central region of the cluster, which has a solid-state density to the moment of the arrival of the main laser pulse.

Detection of the spectra of multicharged ions with time resolution and the determination of the parameters of the hot component of the plasma in the case of the magnetic implosion of multiwire arrays

The dynamics of the hot component of the plasma of imploding multiwire arrays has been analyzed using the time behavior of the X-ray spectral lines of multicharge ions. The spectra of H- and He-like aluminum ions with nanosecond time resolution have been detected using electron-optical chronography in experiments on the implosion of multiwire arrays by mega-ampere currents. The simultaneous appearance of the resonance lines of H- and He-like ions implies that the hot plasma whose electron temperature is higher than 0.5 keV has existed on the axis before the implosion of the main mass of the liner. The further dynamics of the intensity of the lines is primarily attributed to an increase in the mass of the emitting plasma.

Wavelength-dispersive x-ray fluorescence spectrometric determination of tantalum in columbite-tantalite using TaKα and an LiF 420 analysing crystal

The paper proposes a simple, accurate, precise, and rapid method for determining the high atomic number (Z) major-element, tantalum (Z = 73), in the rare mineral, columbite [(Fe,Mn) (Nb,Ta)2O6] — tantalite [(Fe,Mn) (Ta,Nb)2O6], by wavelength-dispersive x-ray fluorescence spectrometry (WDXRFS). The other major-element in columbite-tantalite is the lower atomic number niobium (Z = 41). The method uses the characteristic radiation, TaKα, and an LiF 420 analysing crystal, to overcome the problems associated with the serious x-ray spectral-line interference of the secondorder NbKα and NbKβ with the first-order TaLα1 and TaLβ1 respectively.

Signature of externally introduced laser fields in X-ray emission of multicharged ions

Theory predicts that the presence of strong single-frequency electric fields results in appearance of satellite or dip structures in X-ray spectral lines emitted from hot dense plasmas. Emission from multicharged ions is measured to determine the effects of laser field. A ps-laser beam was split into two parts: the first created an expanding plasma, while the second, which was temporally synchronized, irradiated the plasma at a varying distances in a direction perpendicular to the target normal. The field introduced by the second beam perturbed the plasma environment in the vicinity of radiators. The spatially resolved X-ray spectra were recorded using the high-resolution toroidally bent crystal spectrometer combined with a CCD detector. Spectrally resolved features are observed in broadened Al Heβ line profiles that are consistent with predicted spectra. The predicted spectra are derived from a combination of hydrodynamic plasma modeling post-processed by theoretical models that include the effect of externally introduced laser fields. The possible mixing of higher-intensity fields is qualitatively explained by a combination of fluid and one-dimensional PIC simulations that indicate redistribution of the fields and density fluctuations due to a presence of parametric instabilities.

General Relativity studies through X-ray spectroscopy of the Fe (and others) K α fluorescent lines

I briefly review in this paper the main observational properties of relativistically broadened X-ray spectral lines in Galactic Black Holes and Active Galactic Nuclei, and the (scanty) estimates of their frequency in the corresponding parent populations. The available measurements allow us to derive some constraints on the black hole spin and mass, and on the accretion disk geometry and illumination.

X-ray modulation transfer functions of photostimulable phosphor image plates and scanners

The modulation transfer functions of two types of photostimulable phosphor image plates were determined in the 10 keV to 50 keV x-ray energy range using a resolution test pattern with up to 10 line pairs per mm (LP/mm) and a wavelength dispersive x-ray spectrometer. Techniques were developed for correcting for the partial transmittance of the high energy x rays through the lead bars of the resolution test pattern, and the modulation transfer function (MTF) was determined from the measured change in contrast with LP/mm values. The MTF was convolved with the slit function of the image plate scanner, and the resulting point spread functions (PSFs) were in good agreement with the observed shapes and widths of x-ray spectral lines and with the PSF derived from edge spread functions. The shapes and the full width at half-maximum (FWHM) values of the PSF curves of the Fuji Superior Resolution (SR) and Fuji Maximum Sensitivity (MS) image plate detectors, consisting of the image plate and the scanner, determined by the three methods gave consistent results: The SR PSF is Gaussian with 0.13 mm FWHM, and the MS PSF is Lorentzian with 0.19 mm FWHM. These techniques result in the accurate determination of the spatial resolution achievable using image plate and scanner combinations and enable the optimization of spatial resolution for x-ray spectroscopy and radiography.

A High-Velocity Transient Outflow in η Carinae

We analyze velocity profiles of the X-ray spectral lines emitted by the η Carinae (η Car) stellar binary at four epochs, just before the X-ray minimum (associated with periastron) and more than 2 years before the minimum (~apastron). The profiles are nicely resolved by the HETGS spectrometer on board Chandra. Far from periastron, we find symmetrical lines that are more or less centered at zero velocity. Closer to periastron, the lines broaden, shift toward the blue, and become visibly asymmetric. While the quiescent X-ray emission and slight (<200 km s-1) centroid shifts can be ascribed to the ordinary continuous binary wind interaction and to the orbital velocity of the secondary star, the observed high-velocity emission up to ~2000 km s-1 and the abrupt flares during which it occurs cannot. This leads us to interpret the high-velocity flaring emission as due to a fast collimated outflow of ionized gas.

Directed inward beams of ions in laser produced plasma

We investigated the ion characteristics in picosecond laser plasma at laser radiation intensity of up to 2 × 10 18 W/cm 2 . Our experimental observations of X-ray spectral line profiles confirmed the presence of a great quantity of high-energy ions (∼ 1 MeV) in laser plasma. Besides, by the L yα Doppler profile's red shift we revealed the high-energy ion motion directed inward the target. For this phenomenon we suggest our theoretical model. The high energy tail in the energy spectrum of ions in laser plasmas can be explained by the pinch effect. The effective way for production of beams of charged particles in laser plasmas is the electric drift of these particles in electromagnetic fields generated in the laser-produced plasmas.

X-ray-line plasma satellites of ions in a dense plasma produced by a picosecond laser pulse

X-ray spectral lines of multicharged ions in a solid target interacting with picosecond laser pulses of moderate intensity (~3 × 1017 W cm−2) were measured on the 'Neodim' laser facility. Strong modulations in x-ray Lyα line profiles of hydrogen-like fluorine ions were observed, evidencing the presence of intense plasma oscillations with an amplitude of the electric field larger than 108 V cm−1 and a frequency of about 1015 s−1.

Observations of Solar X-ray Spectra by the DIOGENESS and RESIK Spectrometers Onboard the CORONAS-F Satellite

The first scientific results of the analysis of the X-ray spectra of flares and active regions in the solar corona obtained by Polish-led spectrometers RESIK and DIOGENESS onboard the CORONAS-F satellite are presented. The instruments were designed and made in the Solar Physics Division of the Space Research Center of the Polish Academy of Sciences (SRC PAS, Wroclaw, Poland). The Institute of Terrestrial Magnetism, Ion- osphere, and Radio Wave Propagation (IZMIRAN, Russia) and the Astronomical Institute of the Czech Acad- emy of Sciences also participated in designing the DIOGENESS spectrometer, while IZMIRAN (Russia), Mullard Space Science Laboratory (MSSL, Great Britain), Rutherford Appleton Laboratory (RAL, Great Brit- ain), and Naval Research Laboratory (NRL, United States) contributed to the development of the RESIK spec- trometer. In the paper, we give spectra obtained in a number of previously unstudied spectral ranges and a pre- liminary identification of new spectral lines. The results for the shifts of the X-ray spectral lines observed with the use of a so-called dopplerometer configuration are also presented. Methods for determining the abundances of the rare elements in the solar corona, including chlorine, potassium, and argon, are described.

Constraints on Intracluster Gas Bulk Motions in Clusters of Galaxies with ASCA

The recent detection of Doppler shifts of X-ray spectral lines in the intracluster gas of the Centaurus and Perseus clusters of galaxies with ASCA has raised the question of the frequency of such velocity gradients and their relation to other cluster properties. To address this and improve the sample of ICM velocity gradient candidates we carried out a systematic search of the ASCA archive for clusters with suitable observing conditions that allow full azimuthal mapping of gas velocities near the central regions. Here we present the results of the azimuthal velocity distribution of a sample consisting of the best observed clusters for velocity analysis. Our sample encompasses clusters with different physical and morphological characteristics, including both well-behaved cooling flow and dynamically active clusters. The gas temperatures of the clusters in our sample range from 1.4 to 6.3 keV. We find velocity substructures in ~15% of the clusters in our sample on the order of a few ×103 km s-1. The significance of the velocity gradients' is greater than 99% in Abell 576 and RX J0419.6+0225, the clusters where velocity gradients are most significant. The velocity gradients are consistent with transitory and/or rotational bulk motion. The velocity gradients in these clusters are unlikely to be due to projected temperature anisotropies, ASCA PSF, intrachip gain variations, and flux contamination from other sources. Chandra images of these clusters do not show obvious cluster alignments within the field of view covered by ASCA. We also noticed a high frequency (~50%) of anisotropic temperature gradients in the core of cooling flow clusters, suggesting the presence of frequent dynamical activity in the core of galaxy clusters.

The Phoenix Deep Survey: the radio properties of the hard X-ray-selected sample

The radio properties of hard (2-8 keV) X-ray-selected sources are explored by combining a single 50-ks XMM-Newton pointing with the ultradeep and homogeneous Phoenix radio (1.4-GHz) survey. A total of 43 sources are detected above the X-ray flux limit f X (2-8 keV) = 7.7 x 10 -15 erg s -1 cm -2 , with 14 of them exhibiting radio emission above 40 μJy (3σ). The X-ray-radio matched population lies in the borderline between radio-loud and radio-quiet active galactic nuclei (AGNs) and comprises sources with both soft and hard X-ray spectral properties, suggesting both obscured and unobscured systems. The spectroscopically identified subsample (with a total of six X-ray-radio matches) comprises narrow emission-line AGNs (four) with hard X-ray spectral properties and broad line sources (two) with soft X-ray spectra. We find evidence that the fraction of X-ray-radio matches increases from 20 per cent for sources with a rest-frame column density of N H 10 22 cm -2 their combined spectrum exhibits a soft X-ray component that may be associated with star formation activity, although other possibilities cannot be excluded. We also find that radio-emitting AGNs make up approximately 13-20 per cent of the hard-band X-ray background depending on the adopted normalization.