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From Atoms To Black Holes: Modeling Dense Astrophysical Plasmas

Presentation #321.01 in the session “Laboratory Astrophysics Division (LAD): Soft X-ray Polarization in Space”.

Published onJun 18, 2021
From Atoms To Black Holes: Modeling Dense Astrophysical Plasmas

The detailed modeling of the X-ray spectra from astrophysical sources relies on complete and reliable atomic data provided by the Laboratory Astrophysics community. The need for such accurate atomic quantities becomes more demanding with the arrival of new detectors, which are expected to increase both the volume and the sensitivity of the observational data. In this talk, I will present an overview of new photoionization calculations in the context of modeling accretion disk X-ray spectra, such as those observed from black hole binaries, active galactic nuclei, and neutron stars. In these environments the conditions are extreme, with densities reaching 1018-1022 cm-3. In this regime, the disk density has a dramatic impact on the emitted spectrum, mainly due to the enhancement of the free-free heating rates. However, several other high-density effects have been so far neglected. Prompted by these limitations, we have conducted a program for the systematic upgrade of atomic parameters, accounting for plasma imbedding effects such as electron screening, stimulated processes, suppression of recombination, and enhancement of collisional excitation. I will show the implementation of these new models in fitting X-ray data from several astrophysical sources, which has revealed their significance in the derived abundances, the shape of the X-ray continuum, and provide a possible explanation of the origin of the soft excess in AGN. I will also discuss the diagnostic potential of these models for the future observations that will be delivered by upcoming X-ray missions.

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