High-resolution X-ray spectroscopy of tau Scorpii (B0.2V) with XMM-Newton

We report the analysis of the first high-resolution X-ray spectrum of the B0.2V star τ Scorpii obtained with the Reflection Grating Spectrometers (rg

X-ray/UV campaign on the Mrk 279 outflow: density diagnostics in Active Galactic Nuclei using O V K-shell absorption lines

One of the main problems in modeling the ionised outflows in Active Galactic Nuclei is the unknown distance of the outflowing wind to the central source. Only if the density is known this distance can be determined through the ionisation parameter. Here we study density diagnostics based upon O V transitions. O V is known to have metastable levels that are density dependent. We study the population of those levels under photoionisation equilibrium conditions and determine for which parameter range they can have a significant population. We find that resonance line trapping plays an important role in reducing the critical densities above which the metastable population becomes important. We investigate the K-shell absorption lines from these metastable levels. Provided that there is a sufficient population of the metastable levels, the corresponding K-shell absorption lines are detectable and are well separated from the main absorption line originating from the ground state. We then present the Chandra LETGS spectrum of the Seyfert 1 galaxy Mrk 279 that may show for the first time the presence of these metastable level absorption lines. A firm identification is not yet possible due to both uncertainties in the observed wavelength of the strongest line as well as uncertainties in the predicted wavelength. If the line is indeed due to absorption from O V, then we deduce a distance to the central source of one light week to a few light months, depending upon the importance of additional heating processes.Comment: 10 pages, 8 figures, submitted to Astronomy & Astrophysics, main journa

Science with hot astrophysical plasmas

We present some recent highlights and prospects for the study of hot astrophysical plasmas. Hot plasmas can be studied primarily through their X-ray emission and absorption. Most astrophysical objects, from solar system objects to the largest scale structures of the Universe, contain hot gas. In general we can distinguish collisionally ionised gas and photoionised gas. We introduce several examples of both classes and show where the frontiers of this research in astrophysics can be found. We put this also in the context of the current and future generation of X-ray spectroscopy satellites. The data coming from these missions challenge the models that we have for the calculation of the X-ray spectra

X-Ray Spectra of Early-type Stars Observed with CHANDRA and XMM-Newton}

In this paper I will discuss the temperature, density, and abundance diagnostic tools for X-ray emitting plasmas around early type stars. The methods used are based on individual line fitting, especially applied to the He-like transitions of C, N, O, Ne, Mg, and Si, and on fitting to the total spectrum using SPEX in combination with MEKAL. I will especially focus on biases and possible alternative interpretations for features and observables