Equivalent widths of QSOs

The goal of this search was to use variability as a means of identifying absorption lines arising in gas that is intrinsic to the quasar central engine. We have compared archival Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) spectra of quasars with recent spectra obtained as part of our own snapshot survey of the same objects with the Space Telescope Imaging Spectrograph (STIS).

The intervals between observations are 4-10yr. We primarily focused on the C IV absorption lines, although we also studied other lines available in the same spectra (e.g., Ly{alpha}, N V, O VI).