Invited_talk abstract details

Matter in the immediate vicinity of black holes or neutron stars is subject to the strongest gravitational fields that can be tested with current observatories. X-ray observations of Active Galactic Nuclei, stellar black holes and neutron stars reveal a number of effects of General Relativity working on matter infalling onto these compact objects. Although these observations do not constitute a test of General Relativity in the strong field limit, they do however show (or will be able to show in the future when more sensitive X-ray observatories are operational) strong gravity at work displaying a number of effects: strong gravitational redshifts, innermost stable circular orbits, strong light bending effects and perhaps Lense-Thirring precession. I will show what we have learned about these effects with contemporary X-ray observatories -especially Chandra and XMM-Newton- and will also discuss the expectations from future missions like XEUS.