Jordan, Carole

Contact Email: cj@thphys.ox.ac.uk
Institute: University of Oxford, Dept. of Physics
(Theoretical Physics)
First Coauthor: Stuart A. Sim
Institute: University of Oxford
Second Coauthor: Andrew D. McMurry
Institute: University of Oslo
Subject Area: Stellar Atmospheres, Circumstellar Material
Waveband: Ultraviolet
Technique: Spectroscopy
Presentation: Poster Display
Title: The structure and energy balance of the chromosphere, transition region and corona of $\epsilon$ Eri (K2 V).
Abstract: Observations of $\epsilon$ Eri (K2 V) have been made with the Space Telescope Imaging Spectrograph. In addition to the usual chromospheric and transition region lines, emission in the Fe XII forbidden lines has been discovered (Jordan et al. MNRAS, 332, L5, 2001). The emission line fluxes have been used to develop a new model of the outer atmosphere above the photosphere. We also made use of EUVE line fluxes measured by Laming et al. (ApJ, 462, 948, 1996). An electron pressure of $\simeq 5 \times 10^{15}$ cm^-3 K has been found from the transition region lines of Si III and O IV (Jordan et al. MNRAS, in press). The minimum fractional area occupied by the coronal emission can be found from the critical solution to the energy balance equation, but depends on the ion populations and iron abundance adopted. The fractional area covered by the transition region emission can also be found from energy balance arguments. Line fluxes and profiles have been used together with the MULTI radiative transfer code to develop the new chromospheric model. Heating by wave dissipation is investigated using the widths of optically thin lines.