Radio spectral energy distribution for the red supergiant Antares. The filled red circles and the filled blue diamonds represent the VLA and ALMA data, respectively, and include the statistical 1σ error bars. The continuous lines represents the best-fit line to the underlying data points, while the dashed lines are extrapolations to the remaining data points. The slope on the lines (i.e., the spectral index values) clearly changes from 1.42 above 20 GHz to 0.80 below 8 GHz.