Bibcode
DOI
Testa, Paola; Reale, Fabio; Garcia-Alvarez, David; Huenemoerder, David P.
Referencia bibliográfica
The Astrophysical Journal, Volume 663, Issue 2, pp. 1232-1243.
Fecha de publicación:
7
2007
Revista
Número de citas
20
Número de citas referidas
19
Descripción
We analyze a 96 ks Chandra HETGS observation of the single G-type giant
HR 9024. The high flux allows us to examine spectral line and continuum
diagnostics at high temporal resolution, to derive plasma parameters. A
time-dependent one-dimensional hydrodynamic model of a loop with
half-length L=5×1011 cm (~R*/2) and
cross-sectional radius r=4.3×1010 cm, with a heat pulse
of 15 ks and 2×1011 ergs cm-2 s-1
deposited at the loop footpoints, satisfactorily reproduces the observed
evolution of temperature and emission measure, derived from the analysis
of the strong continuum emission. For the first time we can compare
predictions from the hydrodynamic model with single spectral features,
other than with global spectral properties. We find that the model
closely matches the observed line emission, especially for the hot
(~108 K) plasma emission of the Fe XXV complex at ~1.85
Å. The model loop has L/R*~1/2 and aspect ratio
r/L~0.1, as typically derived for flares observed in active stellar
coronae, suggesting that the underlying physics is the same for these
very dynamic and extreme phenomena in stellar coronae independently of
stellar parameters and evolutionary stage.