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In 2016 we carried out a Swift monitoring program to track the X-ray hardnessvariability of eight type-I AGN over a year. The purpose of this monitoring wasto find intense obscuration events in AGN, and thereby study them by triggeringjoint XMM-Newton, NuSTAR, and HST observations. We successfully accomplishedthis for NGC 3783 in December 2016. We found heavy X-ray absorption produced byan obscuring outflow in this AGN. As a result of this obscuration, interestingabsorption features appear in the UV and X-ray spectra, which are not presentin the previous epochs. Namely, the obscuration produces broad and blue-shiftedUV absorption lines of Ly$\alpha$, C IV, and N V, together with a newhigh-ionisation component producing Fe XXV and Fe XXVI absorption lines. Insoft X-rays, only narrow emission lines stand out above the diminishedcontinuum as they are not absorbed by the obscurer. Our analysis shows that theobscurer partially covers the central source with a column density of few$10^{23}$ cm$^{-2}$, outflowing with a velocity of few thousand km s$^{-1}$.The obscuration in NGC 3783 is variable and lasts for about a month. Unlike thecommonly-seen warm-absorber winds at pc-scale distances from the black hole,the eclipsing wind in NGC 3783 is located at about 10 light days. Our resultssuggest the obscuration is produced by an inhomogeneous and clumpy medium,consistent with clouds in the base of a radiatively-driven disk wind at theouter broad-line region of the AGN.

Chasing obscuration in type-I AGN: discovery of an eclipsing clumpy wind at the outer broad-line region of NGC 3783