Plasma environment effects on K lines of astrophysical interest

Deprince, J.; Bautista, M. A.; Fritzsche, S.; García, Javier A.; Kallman, T. R.; Mendoza, C.; Palmeri, P.; Quinet, Pascal

doi:10.1051/0004-6361/201935075

Cited by 17 publications

(16 citation statements)

References 22 publications

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“…However, atomic data that take the density effect into account are extremely lacking for dense plasmas under solar-interior conditions. Very recently, Deprince et al have investigated plasma-environment effects on the K lines of oxygen (Deprince et al 2019a) and iron (Deprince et al 2019b) ions in accretion disks around black holes. Magnetohydrodynamic simulations show that the electron temperatures and densities span the ranges of 10 5 -10 7 K and 10 18 -10 22 cm −3 , respectively (Schnittman et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Screening potential and continuum lowering in a dense plasma under solar-interior conditions

Zeng

Cheng

et al. 2020

A&A

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An accurate description of the screening potential induced by a hot, dense plasma is a fundamental problem in atomic physics and plasma physics, and it plays a pivotal role in the investigation of microscopic atomic processes and the determination of macroscopic physical properties, such as opacities and equations of state as well as nuclear fusion cross sections. Recent experimental studies show that currently available analytical models of plasma screening have difficulty in accurately describing the ionization-potential depression, which is directly determined by the screening potential. Here, we propose a consistent approach to determine the screening potential in dense plasmas under solar-interior conditions from the free-electron micro-space distribution. It is assumed that the screening potential for an ion embedded in a dense plasma is predominately determined by the free electrons in the plasma. The free-electron density is obtained by solving the ionization-equilibrium equation for an average-atom model to obtain the average degree of ionization of the plasma. The proposed model was validated by comparing the theoretically predicted ionization-potential depression of a solid-density Si plasma with recent experiments. Our approach was applied to investigate the screening potential and ionization-potential depression of Si plasmas under solar-interior conditions over a temperature range of 150–500 eV and an electron-density range of 5.88 × 1022–3.25 × 1024 cm−3. It can be easily incorporated into atomic-structure codes and used to investigate basic atomic processes, such as photoionization, electron-ion collisional excitation and ionization, and Auger decay, in a dense plasma.

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Section: Introductionmentioning

confidence: 99%

Screening potential and continuum lowering in a dense plasma under solar-interior conditions

Zeng

Cheng

et al. 2020

A&A

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“…The density effects on the atomic thresholds (ionization potential and K edge), Kα wavelengths and A-values, and Auger rates of oxygen and iron ions have been studied by [40][41][42][43][44][45]. The atom is assumed to be embedded in a weakly coupled plasma represented in the Multi-Configuration Dirac-Fock (MCDF) method with a time-independent Debye-Hückel screened Dirac-Coulomb Hamiltonian:…”

Section: Continuum Loweringmentioning

confidence: 99%

“…We have recently introduced high-density (n e > 10 18 cm −3 ) effects in the XSTAR database, which come into play in the reflection spectra of the inner region of the accretion disks around compact objects (e.g., black-hole candidates and neutron stars): continuum lowering [40][41][42][43][44][45]; dielectronic recombination suppression [48,49]; collisional ionization; three-body recombination; and stimulated emission. Since the Fe abundance is a key measure of line reprocessing in reflection models [50], we are now in a good position to test if the neglect of such high-density effects is responsible for the anomalously high abundances recurrently derived [51].…”

Section: Introductionmentioning

confidence: 99%

The XSTAR Atomic Database

Mendoza¹,

Bautista²,

Deprince³

et al. 2021

Atoms

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We describe the atomic database of the xstar spectral modeling code, summarizing the systematic upgrades carried out in the past twenty years to enable the modeling of K-lines from chemical elements with atomic number Z≤30 and recent extensions to handle high-density plasmas. Such plasma environments are found, for instance, in the inner region of accretion disks round compact objects (neutron stars and black holes), which emit rich information about the system’s physical properties. Our intention is to offer a reliable modeling tool to take advantage of the outstanding spectral capabilities of the new generation of X-ray space telescopes (e.g., xrism and athena) to be launched in the coming years. Data curatorial aspects are discussed and an updated list of reference sources is compiled to improve the database provenance metadata. Two xstar spin-offs—the ISMabs absorption model and the uaDB database—are also described.

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“…We take into account density effects on the spectroscopic levels by implementing the results of atomic structure calculated by Deprince et al (2019aDeprince et al ( , 2019bDeprince et al ( , 2020a. These authors carried out ab initio calculations of the structure of all stages of oxygen and iron ions using the multiconfiguration Dirac-Fock code together with a time-averaged Debye-Hückel potential to represent the plasma effects.…”

Section: Atomic Structure At High Densitymentioning

confidence: 99%

Photoionization Models for High-density Gas

Kallman

Bautista

Deprince

et al. 2021

ApJ

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Relativistically broadened and redshifted 6.4-6.9 keV iron K lines are observed from many accretion powered objects, including X-ray binaries and active galactic nuclei. The existence of gas close to the central engine implies large radiation intensities and correspondingly large gas densities if the gas is to remain partially ionized. Simple estimates indicate that high gas densities are needed to allow for the survival of iron against ionization. These are high enough that rates for many atomic processes are affected by mechanisms related to interactions with nearby ions and electrons. Radiation intensities are high enough that stimulated processes can be important. Most models currently in use for interpreting relativistic lines use atomic rate coefficients designed for use at low densities and neglect stimulated processes. In our work so far we have presented atomic structure calculations with the goal of providing physically appropriate models at densities consistent with line-emitting gas near compact objects. In this paper we apply these rates to photoionization calculations, and produce ionization balance curves and X-ray emissivities and opacities that are appropriate for high densities and high radiation intensities. The final step in our program will be presented in a subsequent paper in which model atmosphere calculations will incorporate these rates into synthetic spectra.Unified Astronomy Thesaurus concepts: X-ray astronomy (1810); Atomic physics (2063); X-ray observatories (1819); Atomic spectroscopy (2099)

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Plasma environment effects on K lines of astrophysical interest

Cited by 17 publications

References 22 publications

Screening potential and continuum lowering in a dense plasma under solar-interior conditions

Screening potential and continuum lowering in a dense plasma under solar-interior conditions

The XSTAR Atomic Database

Photoionization Models for High-density Gas

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