Dear all,
please find below the links to a couple of new papers that may be of interest to some of you.
The first one is on "Temperature distribution of a non-flaring active region from simultaneous Hinode XRT and EIS observations", and it has just been accepted to ApJ. We discuss the complementary diagnostics from the two instruments, some insights into their cross-calibration, and the effects of the assumed abundances on the results.
The other paper is a short review on "Element abundances in X-ray emitting plasmas in stars" that will soon be published on Space Science Reviews. I know it's a bit off topic, but I thought some of you might be interested in a brief review of recent studies of abundances in stellar coronae. Also, in the paper I'm trying to discuss the findings from solar and stellar abundance studies in a unified context.
Thanks!
cheers, Paola
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"Temperature distribution of a non-flaring active region from simultaneous Hinode XRT and EIS observations" Testa P., Reale F., Landi E., DeLuca, E.E., Kashyap V., ApJ, in press
You can download the paper from http://arxiv.org/abs/1012.0346
Abstract: We analyze coordinated Hinode XRT and EIS observations of a non-flaring active region to investigate the thermal properties of coronal plasma taking advantage of the complementary diagnostics provided by the two instruments. In particular we want to explore the presence of hot plasma in non-flaring regions. Independent temperature analyses from the XRT multi-filter dataset, and the EIS spectra, including the instrument entire wavelength range, provide a cross-check of the different temperature diagnostics techniques applicable to broad-band and spectral data respectively, and insights into cross-calibration of the two instruments. The emission measure distribution, EM(T), we derive from the two datasets have similar width and peak temperature, but show a systematic shift of the absolute values, the EIS EM(T) being smaller than XRT EM(T) by approximately a factor 2. We explore possible causes of this discrepancy, and we discuss the influence of the assumptions for the plasma element abundances. Specifically, we find that the disagreement between the results from the two instruments is significantly mitigated by assuming chemical composition closer to the solar photospheric composition rather than the often adopted "coronal" composition (Feldman 1992). We find that the data do not provide conclusive evidence on the high temperature (log T[K] >~ 6.5) tail of the plasma temperature distribution, however, suggesting its presence to a level in agreement with recent findings for other non-flaring regions.
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"Element abundances in X-ray emitting plasmas in stars" Testa P., Space Science Reviews, in press
http://arxiv.org/abs/1012.0343
Abstract: Studies of element abundances in stars are of fundamental interest for their impact in a wide astrophysical context, from our understanding of galactic chemistry and its evolution, to their effect on models of stellar interiors, to the influence of the composition of material in young stellar environments on the planet formation process. We review recent results of studies of abundance properties of X-ray emitting plasmas in stars, ranging from the corona of the Sun and other solar-like stars, to pre-main sequence low-mass stars, and to early-type stars. We discuss the status of our understanding of abundance patterns in stellar X-ray plasmas, and recent advances made possible by accurate diagnostics now accessible thanks to the high resolution X-ray spectroscopy with Chandra and XMM-Newton.