Example of two H II region candidates with positive and negative in-band spectral index, as discussed in Sect. 5.2. The top two rows show the 8 sub-bands of the GLOSTAR image. The bottom-left panel shows the averaged image at 5.8 GHz used to extract the source, and the bottom-right panel shows the in-band spectral index fitting for the two compact H II regions candidates: the solid line for G024.7897 (Y_factor = 1.02) with α = 1.43 ± 0.02 and the dashed line for G024.7888 (Y_factor = 1.97) with α = −0.55 ± 0.04. The FWHM beam of GLOSTAR in B-configuration (1.0″) is indicated by the white circles in the lower-left corner of each image. There is a clear trend that the fluxes increase and decrease as the increasing frequencies in the sub-bands for G024.7897 and G024.7888 respectively.