16842

Obscuring outflows are remarkably different from the warm-absorber outflows in AGN. They exhibit large columns of high-velocity gas close to the accretion disk. They shield the X-ray radiation comma which has important implications for the launching of outflows. They were first discovered in NGC 5548 thanks to simultaneous X-ray and UV observations in 2013. Recent Swift monitoring of NGC 5548 points to remarkable long-term changes in the strength of X-ray obscuration in NGC 5548. In order to study this change comma simultaneous X-ray and UV high-resolution spectroscopy is required. Therefore comma we propose simultaneous Chandra-HETG (150 ks) and HST-COS (2 orbits) observations to help us address existing questions about the origin and physical structure of the long-lasting obscuration in NGC 5548.