The Sloan Digital Sky Survey Reverberation Mapping Project: the CIV
  Blueshift, Its Variability, and Its Dependence Upon Quasar Properties
  We use the multi-epoch spectra of 362 quasars from the Sloan Digital Sky
Survey Reverberation Mapping project to investigate the dependence of the
blueshift of CIV relative to MgII on quasar properties. We confirm that
high-blueshift sources tend to have low CIV equivalent widths (EWs), and that
the low-EW sources span a range of blueshift. Other high-ionization lines, such
as HeII, also show similar blueshift properties. The ratio of the line width
(measured as both the full-width at half maximum and the velocity dispersion)
of CIV to that of MgII increases with blueshift. Quasar variability might
enhance the connection between the CIV blueshift and quasar properties (e.g.,
EW). The variability of the MgII line center (i.e., the wavelength that bisects
the cumulative line flux) increases with blueshift. In contrast, the CIV line
center shows weaker variability at the extreme blueshifts. Quasars with the
high-blueshift CIV lines tend to have less variable continuum emission, when
controlling for EW, luminosity, and redshift. Our results support the scenario
that high-blueshift sources tend to have large Eddington ratios.
