2004MNRAS.354.1093O

Time-dependent numerical simulations of the Kα complex of Fexxv are carried out as a function of temperature-density-radiation field variations in high-temperature astrophysical and laboratory plasmas. In addition to several well-known features, the transient and steady-state spectra reveal the effects due to (a) time-dependent thermal and non-thermal radiation fields, (b) photo- and collisional excitation and ionization, and (c) high densities, on the `quartet' of principal w, x, y, z lines, and dielectronic satellites. The highly detailed models show precisely how, assuming a temporal-temperature correlation, the X-ray intensity varies between 6.6 and 6.7 keV and undergoes a `spectral inversion' in the w and z line intensities, characterizing an ionization- or a recombination-dominated plasma. The dielectronic satellite intensities are the most temperature-dependent features, but insensitive to density variations, and significantly contribute to the Kα complex for T < 6.7 keV leading to asymmetric profiles. The 6.7-keV Kα complex should be a potential diagnostic of X-ray flares in active galactic nuclei, afterglows in gamma-ray bursts, and other non-equilibrium sources with the high-resolution measurements possible from the upcoming mission Astro-E2. It is also shown that high electron densities attenuate the line intensities in simulations relevant to laboratory plasmas, such as in inertial confinement fusion, laser, or magnetic Z-pinch devices.