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Title: Study of opacity effects in the corona of active stars
Author: Matranga, M.
ISNI:       0000 0001 3621 3129
Awarding Body: Queen's University Belfast
Current Institution: Queen's University Belfast
Date of Award: 2008
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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
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available