Quasi-periodic features due to clumps orbiting around a black hole

The expected Fourier power-spectrum density is examined with regard to the shape and quality factor Q of features which are predicted to appear in a signal from clumps orbiting near a marginally stable orbit of a compact body. It is shown that clumps distributed randomly in a narrow range of radii produce quasi-periodic oscillations with Q approximate to 10(2), similar to those observed in many low-mass X-ray binaries.