IUE observations of the eclipsing binary system HR 6902 obtained at various epochs spread over four years indicate the presence of warm circumstellar material enveloping the G9 IIb primary .
The spectra show Si iv and C iv absorption up to a distance of 3.3 giant radii ( { R _ { g } } ) .
Line ratio diagnostics yields an electron temperature of \sim 78 000 K which appears to be constant over the observed height range .

Applying a least square fit absorption line analysis we derive column densities as a function of height .
We find that the inner envelope ( < 3 { R _ { g } } ) of the bright giant is consistent with a hydrostatic density distribution .
The derived line broadening velocity of \sim 70 { km s ^ { -1 } } is sufficient to provide turbulent pressure support for the required scale height .
However , an improved agreement with observations over the whole height regime including the emission line region is obtained with an outflow model .
We demonstrate that the common \beta power-law as well as a P \propto \rho wind yield appropriate fit models .
Adopting a continuous mass outflow we obtain a mass-loss rate of \dot { M } = 0.8 - 3.4 \times 10 ^ { -11 } M _ { \odot } { yr ^ { -1 } } depending on the particular wind model .

The emission lines observed during total eclipse are attributed mostly to resonance scattering of B star photons in the extended envelope of the giant .
By means of a multi-dimensional line formation study we show that the global envelope properties are consistent with the wind models derived from the absorption line analysis .
We argue that future high resolution UV spectroscopy will resolve the large-scale velocity structure of the circumstellar shell .
As an illustration we present theoretical Si iv and C iv emission profiles showing model-dependent line shifts and asymmetries .