6533b826fe1ef96bd12843bb

RESEARCH PRODUCT

The structure of coronal plasma in active stellar coronae from density measurements

P. TestaJ. DrakeG. Peres

subject

sun : coronastars : activitySettore FIS/05 - Astronomia E AstrofisicaX-rays : starlate-typeactivity; coronae; late-type; sun : corona; X-rays : stars; spectroscopic plasma diagnostics [stars]coronaespectroscopic plasma diagnostics

description

We have analyzed high-resolution X-ray spectra of a sample of 22 active stars observed with the High Energy Transmission Grating Spectrometer (HETGS) on Chandra in order to investigate their coronal plasma density, using the lines of the He-like ions O VII, Mg XI, and Si XIII. Si XII lines in all stars of the sample axe compatible with the low-density limit (i.e. n(e) = 10(30) erg/s); O VII lines yield much lower densities of a few 10(10) cm(-3). Our results indicate that the "hot" and "cool" plasma resides in physically different structures. Our findings imply remarkably compact coronal structures, especially for the hotter (similar to 7 MK) plasma emitting the Mg xi lines characterized by coronal surface filling factor, f(MgXI), ranging from 10(-4) to 10(-1), while we find f(OVII) values from a few 10(-3) up to similar to 1 for the cooler (similar to 2 MK) plasma emitting the O VII lines.

yearjournalcountryeditionlanguage
2005-01-01
http://hdl.handle.net/10447/231962