Iron line profiles from black hole accretion discs with spiral velocity structure

Abstract

We calculate the iron line profiles from accretion discs with spiral velocity structures around Schwarzschild black holes. We find that quasi-periodic bumps, step-like features and secondary peaks appear in the profiles. Non-axisymmetry is important for low radial mode spirals. This study is motivated by recent work showing that spiral density waves can result from magnetohydrodynamic instabilities even in non-self-gravitating discs, such as those of active galactic nuclei or X-ray binaries, and by improved spectral resolution of forthcoming X-ray missions.