Post-fit timing residuals as a function of time for the best-fit timing solutions presented in Table 1, considering non-eclipsing binary phases only. Residuals shown in the upper panel are based on TOAs extracted by using a single template profile representative of the full 512-MHz bandwidth at 1.4 GHz, while those in the lower panel are based on TOAs obtained by fitting a template profile with the full frequency resolution to the data. Details on the TOA integration times, frequency bandwidths, and extraction procedures are given in Sect. 2 for the upper panel, and in Sect. 3 for the lower panel. Residuals shown as red squares (resp., blue diamonds) correspond to observations made at 1.4 GHz (resp., 2.1 and 2.5 GHz). In the upper panel (respectively, the lower panel), TOA uncertainties were multiplied by a correction factor (EFAC, see Sect. 2.1), of 1.074 (resp., 1.726).