X-ray Spectral Variability in Seyfert 1 Galaxies

R. Edelson$^1$

$^1$UCLA Department of Physics and Astronomy; Los Angeles, CA 90095-1562, USA


I will review the ways that comparison of different X-ray bands adds a dimension
 to Seyfert 1 variability studies in constraining the physical
parameters and emission mechanisms in Seyfert 1s.  A strong
correlation between variations in the iron line and continuum fluxes
would be expected because the relativistically broadened spectrum are
believed to arise within a few Schwarzschild radii of the center.
However, we find that the line is only weakly or not at all variable
on short time scales, and not correlated with the continuum.  I will
discuss possible ways to reconcile these observations.

Seyfert 1s also generally show stronger variations in softer X-ray
bands, however, this pattern may reverse in the RXTE band for the
extremely variable narrow-line Seyfert 1s.  Such behavior would be
clear evidence for multiple X-ray emission components.  Finally,
there have been claims of measurable interband lags, which could
allow determination of geometrical and causal relations between emissi
on components.  I will focus on the validity of these claims and the
implications if correct.