Spectral model fit with the standard nonthermal power-law model. The black points with error bars represent archival data taken from the literature. The blue points with error bars or downward arrows indicate GMRT 323 MHz measurements from our work. Calibration errors of 10% were added to the statistical errors of the GMRT 323 MHz data points (Chandra et al. 2004). The red lines represent the fitted models. For fits employing the MCMC method, 100 models were randomly selected from the parameter space as red shaded areas to visualize the model uncertainties. There is not enough data in the cases of J2228+0110 and J2245+0024, thus the measurements are given without any fitting. The fitted results are presented in Table 4.