Do optical/UV variations of spectra of Be stars arise from pulsations or structures hanging over them? There is a need for a temperature-sensitive discriminator for circumstellar structures above Be stars to determine whether their UV flux variations are due to occulting structures or photospheric pulsations.

To address this question, we acquired far-UV (SWP camera) echellograms covering λλ1150–2100 from the IUE final archive. For selected B stars we have selected suitably exposed spectra observed within a short timespan, typically 1–3 days. We summed all the valid net fluxes within each of 60 echelle orders and placed them into an order vs. time array. We identify those times corresponding to high and low fluxes over several reference orders and form the quantity 1 - Fmin(λ)/Fmax(λ), for all echelle orders. The result is a low-resolution spectrum sensitive to absorptions at certain wavelengths, either strong lines such as Lyman α and several UV resonance lines or aggregates of metallic lines. All these are potentially sensitive to temperature variations.