NGC 3783 HST COS and STIS spectra near the C iv line. The line transmission model for the new broad C iv absorption component in 2016 is shown in the top panel. The displayed spectra are continuum subtracted and then offset vertically by 2.5 × 10^-14erg cm^-2 s^-1 Å^-1 for each epoch so that the weaker changes in the absorption are more visible. Narrow absorption lines in the blue wing are interstellar Si iiλ1526 and C ivλ1548,1551.