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| Paper: |
Coronal Loop Modeling of ROSAT/PSPC X-ray Spectra from Solar-Type Stars |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
1183 |
| Authors: |
Ventura, R.; Maggio, A.; Peres, G. |
| Abstract: |
In the context of a wide project devoted to the diagnostic of structures in stellar coronae, we have analyzed ROSAT/PSPC X-ray spectra of a selected sample of 8 G-type stars in the solar neighborhood (d< 25 pc). We fitted the X-ray spectra with a few models: the usual two-temperature isothermal model and the more physically detailed one- and two-loop models, in order to compare the diagnostic power coming from the different approaches. The results point out that the one-loop fitting provides acceptable chi^2 values, but it yields, in the majority of the cases, unacceptable long loops, namely, orders of magnitude larger than the stellar radius. A better physical insight on the observed coronae comes from the two-loops model fitting. Two classes of loops with different characteristics seem to dominate the X-ray emission of our sample of solar-like stars: relatively cool loops (T ~= 1.5 - 5 x 10^6 K) with pressures ranging from low (p_0 ~= 2 - 10 dyn cm^{-2}) to relatively high values (p_0 ~= 100 dyn cm^{-2}) and hot loops (T ~= 1 - 3 x 10^7 K) with very high base pressures (p_0 ~= 10^2 - 2.4 x 10^4 dyn cm^{-2}). We discuss these results, their physical implications and possible interpretations. |
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