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Astron. Astrophys. 358, 57-64 (2000) 7. The accretion emissionTo this point the colliding star model does not take into account the fate of all matter ejected by star collisions into the region around the black hole. It is not our purpose to perform here a detailed physics of this matter evolution and emission. Nevertheless, it is important to test here if and how much this plasma can change the results of the previous section. We can easily suppose that part of the plasma ejected into the interstellar medium can stream along different planes towards the central black hole and can be accreted. In this framework two different emission contributions would be present: the hot expanding shells of plasma caused by star collisions and the accretion of the same plasma on the central black hole. The second emission process can be taken into account supposing
that in each collision about ( This picture, although very simplified, can give an order of magnitude of this process even if the real accretion luminosity would be probably lower (since we have chosen an upper limit for the amount of accreting matter) and varying in time (since matter is discontinually injected into the interstellar medium). It is important to take into account that this approximate
treatment is self consistent only if the typical accretion time
If the mean luminosity due to collisions is approximatively
expressed as in Eq. (9) and expression (3) is taken into account, the
above expression for and the total observable luminosity results With this new expression for the cluster emission we have performed
the same computations as in the case without accretion. The same
parameter sets have been used with the only exception that those pairs
(
© European Southern Observatory (ESO) 2000 Online publication: June 26, 2000 ![]() |