Study of opacity effects in the corona of active stars
The aim of this thesis is the search for opacity effects in the coronal line of Fe XVII at 15.01 Angstrom in a sample of active laty-type stars. The detection l1f opacity is crucial in the field of stellar coronae physics as it is one of a few method that allow us to get information on the coronal s...
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Queen's University Belfast
2008
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| Online Access: | http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484987 |
| Summary: | The aim of this thesis is the search for opacity effects in the coronal line of Fe XVII at 15.01 Angstrom in a sample of active laty-type stars. The detection l1f opacity is crucial in the field of stellar coronae physics as it is one of a few method that allow us to get information on the coronal structure within which the X-ray emitting plasma is'magnetically confined. In order to get information about the coronae of the stars. I have analyzed some high resolution spectra ~ t:). provided by the XMM-Newton satellite: in particular, based on the measured emission line fluxes from varyous chemical elements, I have reconstructed the emission measure distribution and i have examined the observed Fe XVII 16.78 Ang/15.01 Ang line ratio as function of the plasma temperature during flare and quiescient phases. The main result of this thesis is that I have found. for the first time using Fe XVII lines. evidence of resonance scattering for the line at 15.01 Ang. in the flare state of AS Dor. I demonstrate the potential of coronal opacity as a diagnostic and I derive a path length of about 8x1 OA8 cm (0.01 R_star) for the coronal scattering layer. This value is 2 orders of magnitude greater than the path lengths determined in stellar transition region and falls within the range of solar coronal loops |
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