RESUMEN
The interpretation of x-ray spectra emerging from x-ray binaries and active galactic nuclei accreted plasmas relies on complex physical models for radiation generation and transport in photoionized plasmas. These models have not been sufficiently experimentally validated. We have developed a highly reproducible benchmark experiment to study spectrum formation from a photoionized silicon plasma in a regime comparable to astrophysical plasmas. Ionization predictions are higher than inferred from measured absorption spectra. Self-emission measured at adjustable column densities tests radiation transport effects, demonstrating that the resonant Auger destruction assumption used to interpret black hole accretion spectra is inaccurate.
RESUMEN
The modeling of X-ray spectra from photoionized astrophysical plasmas has been significantly improved due to recent advancements in the theoretical and numerical frameworks, as well as a consolidated and reliable atomic database of inner-shell transitions for all the relevant ions. We discuss these developments and the current state of X-ray spectral modeling in the context of oxygen cold absorption in the interstellar medium (ISM). Unconventionally, we use high-resolution astrophysical observations to accurately determine line positions, and adjust the theoretical models for a comprehensive interpretation of the observed X-ray spectra. This approach has brought to light standing discrepancies in the neutral oxygen absorption-line positions determined from observations and laboratory measurements. We give an overview of our current efforts to devise a definitive model of oxygen photoabsorption that can help to resolve the existing controversy regarding ISM atomic and molecular fractions.