High-energy observations of black hole binaries with the INTEGRAL satellite

TL;DR

This paper reviews high-energy observations of black hole binaries with INTEGRAL, highlighting the detection of an additional high-energy component above 200 keV and discussing its possible non-thermal origin.

Contribution

It provides new insights into the high-energy spectral components of black hole binaries based on eight years of INTEGRAL data, including observations of three specific systems.

Findings

Detection of an extra component above 200 keV in several systems

Observation of spectral state-dependent high-energy features

Discussion of non-thermal electron contributions in hot plasma

Abstract

Black-hole binaries are important sources through which studying accretion onto compact objects. In the X/gamma-ray domain, these objects show several and complex spectral behaviours and transitions. Based on INTEGRAL observations collected during the last eightyears, we have now a new view on the high energy emission of black-hole binary. An additional component above 200 keV has been observed in a few systems, during either hard/intermediate or low/hard states. The nature of this hard-tail is still debated, as also the one observed in soft states. However, among a number of models, it is usually attributed to the presence of a small fraction of non-thermal electrons in a hot-Comptonising plasma. I review the high energy emission from black hole binary systems and report on some INTEGRAL observations of three different objects: 1E 1740.7-2942, GX 339-4, Cyg X-1.