Origin of power-law X-ray emission in the steep power-law state of X-ray binaries

Li-Hong Yan, Jian-Cheng Wang


We present a new explanation for the origin of the steep power-law (SPL) state of X-ray binaries. The power-law component of X-ray emission is the synchrotron radiation of relativistic electrons in highly magnetized compact spots orbiting near the inner stable circular orbit of a black hole. It has a hard spectrum that extends to above MeV energies, which is determined by the electron acceleration rate. These photons are then down-scattered by the surrounding plasma to form an observed steep spectrum. We discuss the relevance of the model to high-frequency quasi-periodic oscillations and the extremely high luminosity of the SPL state.


accretion, accretion disks — black hole physics — radiation mecha- nisms: nonthermal — X-rays: binaries

Full Text:



  • There are currently no refbacks.

Print ISSN: 1674-4527

Online ISSN: 2397-6209