Year: 2017
Type: review
Abstract: We review observations of ultraluminous X-ray sources (ULXs). X-ray spectroscopic and timing studies of ULXs suggest a new accretion state distinct from those seen in Galactic stellar-mass black hole binaries. The detection of coherent pulsations indicates the presence of neutron-star accretors in three ULXs and therefore apparently super-Eddington luminosities. Optical and X-ray line profiles of ULXs and the properties of associated radio and optical nebulae suggest that ULXs produce powerful outflows, also indicative of super-Eddington accretion. We discuss models of super-Eddington accretion and their relationship to the observed behaviors of ULXs. We review the evidence for intermediate-mass black holes (IMBHs) in ULXs. We consider the implications of ULXs for super-Eddington accretion in active galactic nuclei, heating of the early Universe, and the origin of the black hole binary recently detected via gravitational waves.
Authors: Philip Kaaret, Hua Feng, Timothy P. Roberts
Institutions: University of Iowa, Tsinghua University, Durham University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Awards: G3050355085, G4329979236
OpenAlex ID: W165507508