Ubiquitous equatorial accretion disc winds in black hole soft states

TL;DR

This paper demonstrates that highly ionised accretion disc winds are a universal feature in the soft states of Galactic Black Holes, with an equatorial geometry and significant implications for accretion and jet physics.

Contribution

It reveals the ubiquity and geometry of accretion disc winds in black hole soft states, highlighting their potential role in accretion processes and jet quenching.

Findings

Winds have mass outflow rates comparable to accretion rates.

Winds are observed only in high-inclination sources.

Higher wind ionisation correlates with harder spectral states.

Abstract

High resolution spectra of Galactic Black Holes (GBH) reveal the presence of highly ionised absorbers. In one GBH, accreting close to the Eddington limit for more than a decade, a powerful accretion disc wind is observed to be present in softer X-ray states and it has been suggested that it can carry away enough mass and energy to quench the radio jet. Here we report that these winds, which may have mass outflow rates of the order of the inner accretion rate or higher, are an ubiquitous component of the jet-free soft states of all GBH. We furthermore demonstrate that these winds have an equatorial geometry with opening angles of few tens of degrees, and so are only observed in sources in which the disc is inclined at a large angle to the line of sight. The decrease in Fe XXV / Fe XXVI line ratio with Compton temperature, observed in the soft state, suggests a link between higher wind ionisation and harder spectral shapes. Although the physical interaction between the wind, accretion flow and jet is still not fully understood, the mass flux and power of these winds, and their presence ubiquitously during the soft X-ray states suggests they are fundamental components of the accretion phenomenon.