Top: example model radio light curves at radio frequencies of 3 GHz (black), 10 GHz (blue), and 30 GHz (red), calculated for our best-fitting parameters for V1324 Sco (Table 4). The light curve does not include thermal emission from the cold central shell or other sources of photoionized ejecta. Bottom: measured spectral index β between the 3 and 10 GHz bands (red) and the 10 and 30 GHz bands (blue). The times of light-curve maxima are marked with symbols for 3 GHz (circle), 10 GHz (square), and 30 GHz (triangle). The plateau at β = 2 at early times corresponds to when the photoionized layer ahead of the shock is still optically thick.