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(13) cm(-3)); Mg XI lines reveal the presence of high plasma densities up to a few 10(12) cm(-3) for most of the sources with higher X-ray luminosity (>= 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.

Testa, P., Drake, J.J., Peres, G. (2005). The structure of coronal plasma in active stellar coronae from density measurements. In Proceedings of the 13th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun.

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

TESTA, Paola;PERES, Giovanni
2005-01-01

Abstract

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(13) cm(-3)); Mg XI lines reveal the presence of high plasma densities up to a few 10(12) cm(-3) for most of the sources with higher X-ray luminosity (>= 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.
2004
13th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun
Hamburg, GERMANY
JUL 05-09, 2004
13th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun
2005
4
Testa, P., Drake, J.J., Peres, G. (2005). The structure of coronal plasma in active stellar coronae from density measurements. In Proceedings of the 13th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun.
Proceedings (atti dei congressi)
Testa, P.; Drake, J. J.; Peres, G.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10447/231962
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