Spectral Analysis Of X-ray Emission Research Articles

Homogeneous, Micron-Scale High-Energy-Density Matter Generated by Relativistic Laser-Solid Interactions.

Short-pulse, laser-solid interactions provide a unique platform for studying complex high-energy-density matter. We present the first demonstration of solid-density, micron-scale keV plasmas uniformly heated by a high-contrast, 400nm wavelength laser at intensities up to 2×10^{21} W/cm^{2}. High-resolution spectral analysis of x-ray emission reveals uniform heating up to 3.0keV over 1 μm depths. Particle-in-cell simulations indicate the production of a uniformly heated keV plasma to depths of 2 μm. The significant bulk heating and presence of highly ionized ions deep within the target are attributed to the few MeV hot electrons that become trapped and undergo refluxing within the target sheath fields. These conditions enabled the differentiation of atomic physics models of ionization potential depression in high-energy-density environments.

Unveiling pure-metal ejecta X-ray emission in supernova remnants through their radiative recombination continuum

Context. Spectral analysis of X-ray emission from ejecta in supernova remnants (SNRs) is hampered by the low spectral resolution of CCD detectors, which typically creates a degeneracy between the best-fit values of chemical abundances and the plasma emission measure. The combined contribution of shocked ambient medium and ejecta to the emerging X-ray emission further complicates the determination of the ejecta mass and chemical composition. This degeneracy leads to big uncertainties in mass estimates and can introduce a bias in the comparison between the ejecta chemical composition derived from the observations and the yields predicted by explosive nucleosynthesis models. Aims. We explore the capabilities of present and future spectral instruments with the aim of identifying a spectral feature that may allow us to discriminate between metal-rich and pure-metal plasmas in X-ray spectra of SNRs. Methods. We studied the behavior of the most common X-ray emission processes of an optically thin plasma in the high-abundance regime. We investigated spectral features of bremsstrahlung, radiative recombination continua (RRC), and line emission, by exploring a wide range of chemical abundances, plasma temperatures, and ionization parameters. We then synthesized X-ray spectra from a state-of-the-art 3D hydrodynamic simulation of Cas A, by using the response matrix from the Chandra ACIS-S charged-coupled device detector and that of the XRISM/Resolve X-ray calorimeter spectrometer. Results. We found that a bright RRC shows up when the plasma is made of pure-metal ejecta, and a high spectral resolution is needed to actually identify this ejecta signature. We tested and verified the applicability of our novel diagnostic tool and we propose a promising target for the future detection of such spectral feature: the southeastern Fe-rich clump of Cas A. Conclusions. While there is no way to unambiguously reveal pure-metal ejecta emission with CCD detectors, X-ray calorimeters will be able to pinpoint the presence of pure-metal RRC and to recover correctly absolute mass and the chemical composition of the ejecta, opening a new window on the link between progenitor star, supernova and SNRs.

Possible Phase-dependent Absorption Feature in the X-Ray Spectrum of the Middle-aged PSR J0659+1414

Abstract We report on the energy-resolved timing and phase-resolved spectral analysis of X-ray emission from PSR J0659+1414 observed with XMM-Newton and NuSTAR. We find that the new data rule out the previously suggested model of the phase-dependent spectrum as a three-component (two blackbodies + power law) continuum, which shows large residuals between 0.3 and 0.7 keV. Fitting neutron star atmosphere models or several blackbodies to the spectrum does not provide a better description of the spectrum and requires spectral model components with unrealistically large emission region sizes. The fits improve significantly if we add a phase-dependent absorption feature with central energy 0.5–0.6 keV and equivalent width up to ≈50 eV. We detected the feature for about half of the pulse cycle. Energy-resolved pulse profiles support the description of the spectrum with a three-component continuum and an absorption component. The absorption feature could be interpreted as an electron cyclotron line originating in the pulsar magnetosphere and broadened by the nonuniformity of the magnetic field along the line of sight. The significant phase variability in the thermal emission from the entire stellar surface may indicate multipolar magnetic fields and a nonuniform temperature distribution. The strongly pulsed nonthermal spectral component detected with NuSTAR in the 3–20 keV range is well fit by a power-law model with a photon index Γ = 1.5 ± 0.2.

Spectral analysis of x-ray emission created by intense laser irradiation of copper materials

We have measured the x-ray emission, primarily from K(α),K(β), and He(α) lines, of elemental copper foil and "foam" targets irradiated with a mid-10(16) W/cm(2) laser pulse. The copper foam at 0.1 times solid density is observed to produce 50% greater He(α) line emission than copper foil, and the measured signal is well-fit by a sum of three synthetic spectra generated by the atomic physics code FLYCHK. Additionally, spectra from both targets reveal characteristic inner shell K(α) transitions from hot electron interaction with the bulk copper. However, only the larger-volume foam target produced significant K(β) radiation, confirming a lower bulk temperature in the higher volume sample.

X-ray emission properties from Circinus X-1

The X-ray activity of Circinus X-1, a periodically flaring source, was studied using observational data from the all-sky monitor onboard the Rossi X-ray Timing Explorer orbital observatory in the 2–12 keV energy band. The cross-correlation analysis of the 1 day averaged data set obtained in 2001 has confirmed the fundamental 16.6 day orbital period. The variability pattern of source emission in September–November 2005 has a complicated structure that may be explained by X-ray emission pressure on the accretion disc and periodically ejected matter. The spectral analysis of X-ray emission has revealed the source behaviour in high- and low-activity states that may be caused by differential absorption of emission by the dynamically changed environment in a close binary system.

A model grid for the spectral analysis of X-ray emission in young Type Ia supernova remnants

We address a new set of models for the spectral analysis of the X-ray emission from young, ejecta-dominated Type Ia supernova remnants. These models are based on hydrodynamic simulations of the interaction between Type Ia supernova explosion models and the surrounding ambient medium, coupled to self-consistent ionization and electron heating calculations in the shocked supernova ejecta, and the generation of synthetic spectra with an appropriate spectral code. The details are provided elsewhere, but in this paper we concentrate on a specific class of Type Ia explosion models (delayed detonations), commenting on the differences that arise between their synthetic X-ray spectra under a variety of conditions.