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We reconsider here this source that was previously analyzed in Paper I using Rosat data.

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This relation between the luminosities and the Doppler factors strictly holds for synchrotron and Self-Synchro-Compton (SSC) emissions, while for External Compton emission (EC) we should shift $1/(p+\alpha) \rightarrow 1/(p+1+2 \alpha)$ (Georganopoulos et al. 2001). In such regime of Compton emission it is $0.5 \geq \alpha_{\rm X} \geq 1$, and for ratios of luminosities of 10^3.5 we overestimate  $R_{\delta }$ by a factor $\sim$3.0 if the emission mechanism is EC. This in principle affects the beaming tracks of flat X-ray spectrum sources but does not critically modify our conclusions considering the scatter of the data in Fig. 2 ($\sim$one order of magnitude).

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