Such a path of research can now bring to a more effective testing of the BH
hypotheses because of the newest developments in X-ray observation
techniques. In fact the X-band radiation emitted from AGNs and BHCs, which
has been observed by detectors mounted on satellites like RoSat, ASCA,
Rossi-XTE and SAX, can in principle contain the signatures of BH fields
either in the continuum (from about 1 keV up to some hundreds) or in
the line profiles.
General relativistic effects in emission line
profiles have been already modelled by many authors (for the Kerr
spacetime see for instance: Laor 1991, Kojima 1991, Hameury et
al. 1994, Karas et al. 1995, Bromley et al. 1997, Fanton
et al. 1997, Dabrowski et al. 1997). Observational
evidences have also already been sought, expecially in AGNs, in whose
high energy spectra an iron K feature (around E=6.4 keV)
can often be detected: this is in particular the case of the Seyfert 1
galaxy MGC-6-30-15 observed by ASCA (Tanaka et al. 1995), in which
the line is seen to be very broad and asymmetric.
Not much attention, however, has been paid on the effects on the reflection continuum which is produced along with the iron line following illumination of the disc by a primary X-ray source, to be most probably identified in a hot corona. We consider particularly important to address this matter, that is to self-consistently calculate the shape of iron lines and continuum together, because this will impose further restrictions on physical properties of the system which will thus be less ambiguous, as remarked in part 4.
Therefore we present here some preliminary results of calculations of the relativistic effects on both the reflection continuum and the line profile, obtained with a fully relativistic code in Kerr metric, and shortly discuss the observability of such effects by present and future detectors.