1998A&A...334..188V

As part of a systematic study devoted to the diagnostic of solar-like coronal structures in late-type stars, we have analyzed ROSAT/PSPC X-ray spectra of eight main sequence G-type stars in the solar neighborhood. We have fitted the X-ray spectra adopting two different classes of models: the usual two-component isothermal models and the more physically meaningful hydrostatic loop models. The two-component isothermal models yield fairly acceptable χ² values, however they allow limited physical insight on the stellar coronal structures; on the other hand, the one-loop model fitting provides unreliable long loops, namely orders of magnitude larger than the stellar radius, in the majority of the cases studied. A more realistic physical description of the observed coronae comes from the two-loop modeling approach: two distinct classes of loops with different characteristics seem to dominate the X-ray emission of our sample of G-type stars: relatively cool loops (T_max≃1.5-5x10⁶K) with pressures ranging from relatively low (p₀≃2-10dyn/cm²) to high values (p₀≃100dyn/cm²) and hot loops (T_max≃1-3x10⁷) with very high base pressures (p₀≃10²-2.4x10⁴dyn/cm²). We compare the results and the diagnostic power coming from the different approaches and discuss their physical implications.