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Paper: He II Reverberation in AGN
Volume: 311, AGN Physics with the Sloan Digital Sky Survey
Page: 179
Authors: Bottorff, M.C.; Baldwin, J.A.; Ferland, G.J.; Ferguson, J.W.; Korista, K.T.
Abstract: Observations of emission line variability in the broad line region (BLR) of active galactic nuclei (AGN) show that the response of He II λ1640 to changes in the ionizing continuum of the central engine is three times shorter than that of He II λ4686 and C IV λ1549. Various models invoking radius-dependent pressure laws, locally optimally emitting cloud distributions, anisotropic beaming, and disk obscuration do not reproduce this observation. This suggests that an important component of AGN structure has yet to be explained.
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