## 8. Discussion and conclusionsThe analysis of this paper is based on the working hypothesis that
AGN variability is due to star collisions occurring in the
neighborhood of the central black hole. These collisions will
reproduce the observed AGN luminosities (in the range
erg s It is also important to stress that the agreement between our results and those of Paltani & Courvoisier 1997 is not due to the presence of many parameters in the model, since most of them, as explained in Sect. 5, do not influence the result shown in Fig. 4. In fact, the dispersion of the points in Fig. 4 is only due to different concentrations of stars near the galaxy center, which induce different distributions of collision energies (see Sect. 5). This means that the model presented here is able to fit observations because of the form of the keplerian velocity. Peaked density distributions favor high velocity stars and hence strong collisions. The difference in the event intensity can be estimated by comparing the light curves corresponding to two different configurations present in Fig. 4 having the same collision rate value but different density distribution. The first one is the light curve of Fig. 1; the second one is shown in Fig. 6. The two curves are generated with the same collision rate and hence both have a shape compatible with the observed AGN light curves. A difference in the star density distribution ( and , respectively) produces a big difference in the collision intensity and hence in the produced luminosity, as the vertical scales of the two figures show.
© European Southern Observatory (ESO) 2000 Online publication: June 26, 2000 |