The Spectroscopic Signature of Variability in High-Redshift Quasars
  Using 16,421 spectra from a sample of 340 quasars ($1.62<z<3.30$) from the
SDSS Reverberation Mapping Project, we present an analysis of quasar spectral
variability. We confirm the intrinsic Baldwin Effect and brighter-means-bluer
trends in which emission line strength and color are associated with changes in
luminosity. We then create a composite differential spectrum that captures the
wavelength dependence of quasar variability as a function of change in
luminosity. When using a bandpass around 1740 \AA\ to describe the luminosity,
the differential spectrum follows a power law at longer wavelengths that breaks
blueward of 1700 \AA. However, the shape of the differential spectrum, the
location of the power law break, and the slope of the intrinsic Baldwin Effect
all vary with the choice of bandpass used to define the change in quasar
luminosity. We propose that the observed behavior can be explained by
inhomogeneous accretion or slim accretion disk models where delays in the
reprocessing of incident light on the accretion disk cause local deviations in
temperature from the thin disk model. Finally, we quantify the effects on
cosmology studies due to the variations in the quasar spectrum in the
Lyman-$\alpha$ forest wavelength range. Using the observed spectroscopic
signatures to predict the quasar continuum over the interval $1040 < \lambda <
1200$ \AA, we find that the derived spectral templates can reduce the
uncertainty of the Lyman-$\alpha$ forest continuum level in individual epochs
from 17.2% to 7.7%, near the level where systematic errors in SDSS flux
calibration are expected to dominate.
