Determination of the spectral index for source 140 (G359.784+0.040). Only frequency bands that meet the minimum threshold of 3σ are considered. The solid blue line shows the best-fit model determined by the linear regression. The fitted spectral index is indicated in the upper right corner. The frequencies range from 4.45 GHz to 7.2 GHz. The spectral indices of the full sample are shown in Appendix C.