flux density of J0536-6918. Results of this fitting are given in Table \[tb:grad\]. The second and third columns give the gradient and $x$-intercept of the lines fitted to all data between day 3000 and day 5100 (cf. Fig. \[fg:fluxvar\]). The point of interest here is that there is a systematic increase of the date of intercept with frequency. Especially for the higher frequencies, the intercept is well after the date of first detection of the SNR. This shows that the higher frequencies have a higher relative rate of flux density increase and that the present rate of increase is much higher than that at early times. Note that this effect is seen in both the scaled and unscaled data, so it is not an artifact of the scaling procedure.

As a further check, the data sets were split into two halves, from day 3000 to day 4050 and from day 4050 to day 5100, and straight lines fitted to both halves. Results are tabulated in columns 4 – 7 of Table \[tb:grad\]. The values of reduced $\chi^2$ for the combined fit were computed by treating the two lines as a single model describing the complete data set from day 3000 