Electron density diagnostic potential of the Si x ion and its application in Procyon |
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Authors: | G Y Liang G Zhao J R Shi |
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Institution: | National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China;Beijing Key Laboratory for Nano-Photonics &Nano-Structure, Capital Normal University, Beijing 100037, China |
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Abstract: | Theoretical electron density sensitive line ratios R 1– R 6 of Si x soft X-ray emission lines are presented. We found that these line ratios are sensitive to electron density n e, and the ratio R 1 is insensitive to electron temperature T e. For reliable determination of the electron density of laboratory and astrophysical plasmas, atomic data, such as electron impact excitation rates, are very important. Our results reveal that the discrepancy of the line ratios from different atomic data calculated with the distorted wave (DW) approximation and the R-matrix method is up to 19 per cent at n e= 2 × 108 cm−3 . We applied the theoretical intensity ratio R 1 to the Low Energy Transmission Grating Spectrometer (LETGS) spectrum of the solar-like star Procyon. By comparing the observed value (1.29) with the theoretical calculation, the derived electron density n e is 2.6 × 108 cm−3 , which is consistent with that derived from (C v < 8.3 × 108 cm−3) . When the temperature structure of the Procyon corona is taken into account, the derived electron density increases from n e= 2.6 × 108 to 2.8 × 108 cm−3 . |
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Keywords: | line: identification methods: analytical stars: coronae X-rays: general |
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