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A&A 432, 671-685 (2005)
DOI: 10.1051/0004-6361:20041739
Coronal properties of G-type stars in different evolutionary phases
L. Scelsi1, A. Maggio2, G. Peres1 and R. Pallavicini21 Dipartimento di Scienze Fisiche ed Astronomiche, Sezione di Astronomia, Università di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
e-mail: scelsi@oapa.astropa.unipa.it
2 INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
(Received 27 July 2004 / Accepted 6 November 2004 )
Abstract
We report on the analysis of XMM-Newton observations of three
G-type stars in very different evolutionary phases: the weak-lined T Tauri star
HD 283572
, the Zero Age Main Sequence star
EK Dra
and the
Hertzsprung-gap giant star
31 Com
. They all have high X-ray luminosity
(~1031 erg s-1 for HD 283572 and 31 Com and
~1030 erg s-1 for EK Dra). We compare the Emission Measure
Distributions (
s) of these active coronal sources, derived from
high-resolution XMM-Newton grating spectra, as well as the pattern of
elemental abundances vs. First Ionzation Potential (FIP). We also perform
time-resolved spectroscopy of a flare detected by XMM from EK Dra. We interpret
the observed s as the result of the emission of ensembles of magnetically
confined loop-like structures with different apex temperatures. Our analysis
indicates that the coronae of HD 283572 and 31 Com are very similar in terms of
dominant coronal magnetic structures, in spite of differences in the
evolutionary phase, surface gravity and metallicity. In the case of EK Dra the
distribution appears to be slightly flatter than in the previous two cases,
although the peak temperature is similar.
Key words: X-rays: stars -- stars: activity -- stars: coronae -- stars: individual: 31 Com -- stars: individual: EK Dra -- stars: individual: HD 283572
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