X-ray, UV and optical analysis of supergiants: ε Ori

We present a multi-wavelength (X-ray to optical) analysis, based on non-local thermodynamic equilibrium photospheric+wind models, of the B0 Ia-supergiant: epsilon Ori. The aim is to test the consistency of physical parameters, such as the mass-loss rate and CNO abundances, derived from different spectral bands. The derived mass-loss rate is (M) over dot/root f(infinity) similar to 1.6 x 10(-6) M-circle dot yr(-1) where f(infinity) is the volume filling factor. However, the S IV lambda lambda 1062,1073 profiles are too strong in the models; to fit the observed profiles it is necessary to use f(infinity) < 0.01. This value is a factor of 5 to 10 lower than inferred from other diagnostics, and implies (M) over dot less than or similar to 1 x 10(-7) M-circle dot yr(-1). The discrepancy could be related to porosity-vorosity effects or a problem with the ionization of sulphur in the wind. To fit the UV profiles of NV and O VI it was necessary to include emission from an interclump medium with a density contrast (rho(cl)/rho(ICM)) of similar to 100. X-ray emission in H/He like and Fe L lines was modelled using four plasma components located within the wind. We derive plasma temperatures from 1 x 10(6) to 7 x 10(6) K, with lower temperatures starting in the outer regions (R-0 similar to 3-6 R-*), and a hot component starting closer to the star (R-0 less than or similar to 2.9 R-*). From X-ray line profiles we infer (M) over dot < 4.9 x 10(-7) M-circle dot yr(-1). The X-ray spectrum (>= 0.1 kev) yields an X-ray luminosity L-X similar to 2.0 x 10(-7) L-bol, consistent with the superion line profiles. X-ray abundances are in agreement with those derived from the UV and optical analysis: epsilon Ori is slightly enhanced in nitrogen and depleted in carbon and oxygen, evidence for CNO processed material.