Probing X-ray Emitting Plasma with High Resolution Chandra and XMM-Newton Spectra

Highlights of interesting astrophysical discoveries are reviewed in the context of high resolution X-ray spectroscopy made possible with Chandra and XMM-Newton , and its relevance to atomic physics calculations and measurements is discussed. These spectra have shown that the overlap between astrophysics and atomic physics is stronger than ever, as discoveries of new X-ray lines and edge structure is matching the need for increasingly detailed theoretical calculations and experimental measurements of atomic data. 1. X-ray spectral probes of astrophysical systems at high resolution High resolution X-ray spectroscopy provides a powerful new tool for advancing our understanding of the physical environments of energetic astrophysical systems. As demonstrated with Chandra and XMM spectral studies, the scientific impact is far reaching, encompassing studies of stars, supernova remnants (SNR), X-ray binaries (XRBs), active galactic nuclei (AGN), clusters, and the interstellar and intergalactic medium (respectively ISM and IGM). To give a flavor for some of the newly X-ray discovered spectral features and their relevance to spectral modeling and calculations, I will draw mostly on examples from observations of AGN and XRBs with which I have been involved. See Paerels & Kahn (2003) for a complete review of Chandra and XMM results. 1.1. Narrow emission and absorption lines Narrow (i.e. barely resolved) emission and absorption lines are nearly ubiquitous in the astrophysical sources seen at high resolution. From the lines strengths alone, we can deduce much about the conditions of the plasma, which range from the “X-ray cold” where fluorescent emission and photoionzation prevail to the “X-ray hot” where collisional ionization dominates. From the view of atomic calculations and spectral modeling, the parameterization of the emitters and absorbers are at an advanced state as demonstrated by high resolution spectral studies of the photoionized plasma in Seyfert galaxies (e.g., Sako et al. 2000; Ogle et al. 2000; Branduardi-Raymont et al. 2001; Collinge et al. 2001; Lee et al. 2001, 2002a; Kaspi et al. 2000, 2001, 2002; Brinkman et al. 2002; Kinkhabwala et al. 2002; Blustin et al. 2003; Sako et al. 2003). Specific features which demonstrate the power of high resolution spectroscopy come from the detection of high order (low oscillator strength) resonance absorption lines (i.e. higher than Lyman γ) which are the mark of high optical depth clouds (e.g., Lee et al. 2001; Kaspi et al. 2002). Commonly used atomic codes include Cloudy: Ferland et al. http://www.nublado.org/ 1