Expected linear polarization rates in the continuum due to Rayleigh scattering in a model atmosphere adequate for Betelgeuse (T_eff = 3750 K, log g = 0.5, M = 15M_⊙, v_t = 5 km s⁻¹ and solar composition). Top panel: polarization rates at the fixed wavelentgh of 600 nm as a function of the angular distance μ = cosθ to disk centre. The envelope, beyond the stellar radius, is artificially shown with negative values of μ = cos θ. The thin line gives the actual polarization rate respect to the local intensity. The thick line gives the rate normalized to the intensity at the disk centre, providing a measure of the relative contribution to polarization the integrated polarization signal. Bottom panel: dependence of the polarization rate with wavelength at a fixed distance to disk centre μ = cos θ = 0.