Mewe, Rolf

Contact Email: R.Mewe@sron.nl
Institute: Space Research Organization Netherlands (SRON),
Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
First Coauthor: D. Porquet
Institute: CEA/DSM/DAPNIA, Service d'Astrophysique, CEA Saclay, F-91191 Gif sur Yvette Cedex,
France
Second Coauthor: A.J.J. Raassen
Institute: Space Research Organization Netherlands (SRON),
Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
Research URL:http://www.sron.nl
Subject Area: Atomic Data for Astrophysics
Waveband: X-rays
Technique: Spectroscopy
Presentation: Poster Display
Title: Improved line ratio calculations for He-like ions
Abstract: The new generation of X-ray satellites Chandra (LETGS,HETGS) and XMM-Newton(RGS) provides us with high-resolution and high S/N spectra of a variety of astrophysical sources (stellar coronae, X-ray binaries, AGNs, SNRs ...). A powerful diagnostics for density and temperature based on the line ratios R=f/i and G=(f+i)/r of the three main (resonance r, intercombination i, forbidden f) lines of the He-like triplets was already applied three decades ago to the solar corona, but for a better analysis of the new-generation spectra we have started to recalculate R and G for the He-like ions of C, N, O, Ne, Mg, and Si taking into account all processes playing a role in the various different objects. All excitation and radiative processes between the levels including cascades from dielectronic and radiative recombination have been considered. The best experimental or theoretical values for radiative transition probabilities are used. For the higher-Z ions of Ne, Mg, and Si contributions from blended dielectronic satellite lines to each line of the triplets were included. The influence of an external radiation field on the depopulation of the upper level of f is considered which can be important e.g., for hot OB or F stars (we considered zeta Puppis, Procyon, and Algol). The first calculations were done for plasmas in collisional ionization equilibrium, but will be extended to photo-ionized plasmas (e.g., X-ray binaries, warm absorber in AGNs) and also to transient ionization plasmas (young SNRs), where the innershell ionization of the Li-like ion can contribute significantly to the intensity of the forbidden line.