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We model the ultraviolet spectra of the Seyfert 1 galaxy NGC~5548 obtainedwith the Hubble Space Telescope during the 6-month reverberation-mappingcampaign in 2014. Our model of the emission from NGC 5548 corrects foroverlying absorption and deblends the individual emission lines. Using themodeled spectra, we measure the response to continuum variations for thedeblended and absorption-corrected individual broad emission lines, thevelocity-dependent profiles of Ly$\alpha$ and C IV, and the narrow and broadintrinsic absorption features. We find that the time lags for the correctedemission lines are comparable to those for the original data. Thevelocity-binned lag profiles of Ly$\alpha$ and C IV have a double-peakedstructure indicative of a truncated Keplerian disk. The narrow absorption linesshow delayed response to continuum variations corresponding to recombination ingas with a density of $\sim 10^5~\rm cm^{-3}$. The high-ionization narrowabsorption lines decorrelate from continuum variations during the same periodas the broad emission lines. Analyzing the response of these absorption linesduring this period shows that the ionizing flux is diminished in strengthrelative to the far-ultraviolet continuum. The broad absorption linesassociated with the X-ray obscurer decrease in strength during this same timeinterval. The appearance of X-ray obscuration in $\sim\,2012$ corresponds withan increase in the luminosity of NGC 5548 following an extended low state. Wesuggest that the obscurer is a disk wind triggered by the brightening of NGC5548 following the decrease in size of the broad-line region during thepreceding low-luminosity state.

astrophysical journal/the astrophysical journal

Space Telescope and Optical Reverberation Mapping Project. VIII. Time  Variability of Emission and Absorption in NGC 5548 Based on Modeling the  Ultraviolet Spectrum