000003967 001__ 3967
000003967 005__ 20190128165035.0
000003967 037__ $$aSCART-2019-0094
000003967 100__ $$aDehghanian, M.
000003967 245__ $$aSpace Telescope and Optical Reverberation Mapping Project. X. The Hidden Life of "the Obscurer" in NGC 5548 and Understanding the Absorption-Line Holiday
000003967 260__ $$c2018
000003967 520__ $$aThe flux variations in the emission lines in active galactic nuclei (AGNs) are driven by variations in the ionizing continuum flux --which are usually reflected in the observable UV-optical continuum. The "Reverberation mapping" technique measures the delay between line and continuum variations to determine the size of the line emitting region, this is the basis for measurements of the central black hole mass in AGNs. The Space Telescope and Optical Reverberation Mapping Project (AGN STORM) on NGC 5548 in 2014 is the most intensive multi-wavelength AGN monitoring campaign ever. For most of the campaign, the emission-line variations followed changes in the continuum with a time lag, as expected. However, the lines varied independently of the observed UV- optical continuum during a 60 -- 70 day "holiday." To understand this remarkable phenomenon, we study the intrinsic absorption lines present in NGC 5548. We identify a novel cycle that reproduces the absorption line variability and thus identify the physics that allows the holiday to occur. In our model, variations in this obscurer's line-of-sight covering factor modify the soft X-ray continuum. This leads to changes in the ionization of helium gas in the broad-line region. Ionizing radiation produced by recombining helium then affects the ionization of other species as observed during the AGN STORM holiday. It is likely that any other model which selectively changes the soft X-ray part of the continuum during the holiday can also explain the anomalous emission line behavior observed.
000003967 594__ $$aNO
000003967 700__ $$aFerland, G. J.
000003967 700__ $$aKriss, G. A.
000003967 700__ $$aPeterson, B. M.
000003967 700__ $$aMathur, S.
000003967 700__ $$aMehdipour, M.
000003967 700__ $$aGuzman, F.
000003967 700__ $$aChatzikos, M.
000003967 700__ $$avan Hoof, P. A. M.
000003967 700__ $$aWilliams, R. J. R.
000003967 700__ $$aArav, N.
000003967 700__ $$aBarth, A. J.
000003967 700__ $$aBentz, M. C.
000003967 700__ $$aBisogni, S.
000003967 700__ $$aBrandt, W. N.
000003967 700__ $$aCrenshaw, D. M.
000003967 700__ $$aDalla Bonta, E.
000003967 700__ $$aDe Rosa, G.
000003967 700__ $$aFausnaugh, M. M.
000003967 700__ $$aGelbord, J. M.
000003967 700__ $$aGoad, M. R.
000003967 700__ $$aGupta, A.
000003967 700__ $$aHorne, Keith
000003967 700__ $$aKaastra, J.
000003967 700__ $$aKnigge, C.
000003967 700__ $$aKorista, K. T.
000003967 700__ $$aMc Hardy, I. M.
000003967 700__ $$aPogge, R. W.
000003967 700__ $$aStarkey, D. A.
000003967 700__ $$aVestergaard, M.
000003967 773__ $$pAstrophysical Journal
000003967 8560_ $$fpeter.vanhoof@observatoire.be
000003967 85642 $$ahttps://ui.adsabs.harvard.edu/\#abs/2018arXiv181211578D
000003967 905__ $$asubmitted to
000003967 980__ $$aREFERD