Ultra fast outflows were first discovered in 2003, from the presence of blue-shifted absorption lines from the X-ray spectra of quasars and AGN. The observational evidence for fast outflows will be reviewed, including their statistical occurrence and wider properties from observations with XMM-Newton and Suzaku. New data from large XMM-Newton and NuSTAR programs on the prototype fast outflow AGN, PDS 456 and PG 1211+143 will be shown, where the former shows a fast wide angle outflow and the latter shows highly variable absorption.
The evidence for soft X-ray absorption will also be discussed as well as the possible driving mechanisms of the winds.
Possible Open questions.
What is the statistical occurrence of the outflows. Is their still any doubt about their detection and origins?
How can we measure accurately the energetics of the winds and are they likely to be significant for feedback?
What is the evidence for the ultra fast outflows aside from at iron K?
What is the driving mechanism for the disk wind?
What is the occurrence of the winds amongst the higher luminosity (or higher redshift) QSOs. Will we need Athena to be able to address this?