In the present work we have essentially been able to show that in presence of an accreting BH system the iron edge as well as the lines should be smoothed down ("smearing") and the whole broad-band spectrum should spread out in frequency ("enlargement") because of the energy shift of the photons, that will be more and more pronounced towards both ends of the spectrum with increasing observer inclinations, as a result of the Doppler shift.
Only standard assumptions for the disc physics and structure have been considered here. These assumptions can be changed and more calculations can be easily performed if other accretion models are considered, such as those related with advection dominated flows [ADAF] (see e.g.: Abramowicz et al. 1996; for an updated review: Narayan et al. 1998). Even bimodal accretion flows can be treated, i.e. transitions from one to another regime of accretion in the flow itself (e.g. Dullemond & Turolla 1998), like in the work made by Done et al. (1997) who calculated both line and reflected continuum in the Schwarzschild metric giving evidence to the relativistic smearing, too, with regard to a BHC (Nova Muscae).
Such "non-standard" accretion models can be the subject of much future work. On the same way, in the future it will be important to look for independent confirmations of the estimates of BH-spin and other parameters that one can make looking at the effects on the X-band features. These confirmations can be obtained for instance through variability issues. At this regard, RXTE observations of fast, stable quasi periodic oscillations (QPOs) in BHCs have recently raised much interest, and even an AGN like IRAS 18325-5926 is an excellent case to be studied, because of both the presence of a broad, possibly relativistic iron line (Iwasawa et al. 1995, 1996a) and of a recent claim, based on ASCA observations, that the source shows a periodic variability at about 58 ks.