A new relativistic component of the accretion disk wind in PDS 456

TL;DR

This study uncovers a new, highly relativistic component of the accretion disk wind in quasar PDS 456, detected via hard X-ray observations, revealing a wind velocity of approximately 0.46c and suggesting origins close to the black hole.

Contribution

The paper reports the discovery of a relativistic wind component in PDS 456, detected with NuSTAR and XMM-Newton, which was not previously observed, indicating a faster wind zone near the black hole.

Findings

Detection of a wind with velocity ~0.46c in PDS 456

The relativistic wind is observed during low flux states

The wind may originate close to the black hole at ~10 gravitational radii

Abstract

Past X-ray observations of the nearby luminous quasar PDS 456 (at $z=0.184$) have revealed a wide angle accretion disk wind (Nardini et al. 2015), with an outflow velocity of $\sim-0.25c$. Here we unveil a new, relativistic component of the wind through hard X-ray observations with NuSTAR and XMM-Newton, obtained in March 2017 when the quasar was in a low flux state. This very fast wind component, with an outflow velocity of $-0.46\pm0.02c$, is detected in the iron K band, in addition to the $-0.25c$ wind zone. The relativistic component may arise from the innermost disk wind, launched from close to the black hole at radius of $\sim10$ gravitational radii. The opacity of the fast wind also increases during a possible obscuration event lasting for 50 ks. We suggest that the very fast wind may only be apparent during the lowest X-ray flux states of PDS 456, becoming overly ionized as the luminosity increases. Overall, the total wind power may even approach the Eddington value.