## Loop modeling of coronal X-ray spectra## IV. One- and two-loop model fitting of ROSAT PSPC spectra: three test cases
We present a detailed application of coronal hydrostatic loop
models to fit ROSAT/PSPC X-ray spectra, using three late-type stars,
Procyon (F5 IV - V), Vir
(F6 III), and HR 3625 (F9 V), selected as test cases
showing different activity levels. We present results of the spectral
analysis with models of coronae made of one class of loops or two
classes of loops, and compare them with the results obtained with
two-component isothermal models. The loop model analysis is performed
with a fitting method as accurate as in the case
of the two-temperature modeling, including evaluation of statistical
confidence regions in the model parameter space. We show that the
observed spectra of Procyon and Vir can be
successfully fitted with one-loop models, while two-loop models are
required to fit the spectrum of HR 3625. In the case of Procyon,
for which EUVE spectra are also available, we find that a coronal
density estimate - based on emission line ratios - is consistent with
the results of our one-loop model fitting. The case of HR 3625 is
adopted to illustrate how the confidence regions in the two-loop model
parameter space can be explored and interpreted. Our final results
indicate different coronal conditions for the three selected stars:
Procyon emission is dominated by relatively short
( cm), low pressure (
2 dyn cm
## Contents- 1. Introduction
- 2. The test cases
- 3. Analysis of the X-ray spectra
- 4. Loop modeling applications, results and discussion
- 5. Summary and conclusions
- Acknowledgements
- References
© European Southern Observatory (ESO) 1997 Online publication: May 5, 1998 |