Measurements of the flux density of α Cen A (blue circles) and α Cen B (red circles) with ALMA, with statistical 1σ error bars inside the symbols. Left: assuming that S_ν ∝ ν^α, least-square fits to the Bands 3 to 9 flux densities are shown with dashed lines with the power-law exponent α = dlog S_ν/ dlog ν shown next to them. Right: fits are shown with solid lines, performed as in the left panel, to the data above, and with dotted lines below 200 GHz (~1.5 mm). The ALMA bands, with their central wavelengths, are identified at the bottom of the figure.