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3.5. The Overall continuum spectral energy distribution

Having studied the emission components separately we can now put all these elements together. To do so we present in Fig. 8 the average spectrum obtained by projecting all the data of Fig. 1 onto the frequency axis. Figure 8 also gives the same data but in the form of nu . fnu versus nu. It is striking that the flux per logarithmic interval is nearly constant over more than ten decades of frequency, another way of expressing that to the first order the emission is proportional to nu-1. In the second order, it is striking to see two maxima in the nu . fnu versus nu distribution at roughly the same level, one in the far ultraviolet and the other at about 1MeV.

Integrating the spectrum one can deduce the total flux in the average spectrum and the bolometric luminosity of 3C 273. One finds a total flux of 1.9 . 10-9 ergs s-1cm-2 and assuming isotropic emission, H0 = 50km/(s Mpc), Omega = 1 and q0 = 0.5 one finds a luminosity of 2.2 . 1047ergs s-1. (Türler et al in preparation).

Figure 8

Figure 8. Overall average spectrum of 3C 273 (first panel). This corresponds to a projection onto the frequency axis of all data in figure 1. The bottom panel shows the same data as above but represented as nu . fnu versus nu.

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