Journal Article

Regulation of black-hole accretion by a disk wind during a violent outburst of V404 Cygni

Linares, M., Mooley, K. P., Fender, R. P., Rodriguez, J., Casares, J., Muñoz-Darias, T., Padilla, M. Armas, Charles, P. A., Sánchez, D. Mata, Ponti, G.

2016

Overview

A sustained, neutral wind from the outer accretion disk is observed in the transient black hole V404 Cygni during a violent outburst; this unusual wind, which expands at one per cent of the speed of light and triggers a nebular phase once accretion drops sharply and the ejecta become optically thin, probably regulates the outburst evolution of the black hole. Accretion regulated by a disk wind in V404 Cygni black hole Teo Muñoz-Darias et al . report observations of a sustained outer accretion disk wind in the stellar-mass black hole in the V404 Cygni binary system that is unlike any seen previously. The outflowing wind is neutral, has a large covering factor and expands at 1% of the speed of light. The luminous, but brief, accretion phases shown by transients with large accretion disks imply that this type of outflow could be a previously unknown factor regulating mass accretion onto black holes. Accretion of matter onto black holes is universally associated with strong radiative feedback 1 and powerful outflows 2 . In particular, black-hole transients 3 have outflows whose properties 4 are strongly coupled to those of the accretion flow. This includes X-ray winds of ionized material, expelled from the accretion disk encircling the black hole, and collimated radio jets 5 , 6 . Very recently, a distinct optical variability pattern has been reported in the transient stellar-mass black hole V404 Cygni, and interpreted as disrupted mass flow into the inner regions of its large accretion disk 7 . Here we report observations of a sustained outer accretion disk wind in V404 Cyg, which is unlike any seen hitherto. We find that the outflowing wind is neutral, has a large covering factor, expands at one per cent of the speed of light and triggers a nebular phase once accretion drops sharply and the ejecta become optically thin. The large expelled mass (>10 −8 solar masses) indicates that the outburst was prematurely ended when a sizeable fraction of the outer disk was depleted by the wind, detaching the inner regions from the rest of the disk. The luminous, but brief, accretion phases shown by transients with large accretion disks 2 imply that this outflow is probably a fundamental ingredient in regulating mass accretion onto black holes.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 639/33/34/864 / 639/33/34/867 / Accretion / Accretion disks / Astronomical research / Astronomy / Astrophysics / Binary stars / Black holes / Black holes (Astronomy) / Humanities and Social Sciences / letter / multidisciplinary / Observations / Physics / Science / Stars & galaxies / Stellar winds / Wind