Behaviour of the MgII 2798AA Line Over the Full Range of AGN Variability
  We investigate the responsiveness of the 2798AA Mg II broad emission line in
AGN on timescales of several years. Our study is based on a sample of extremely
variable AGN as well as a broad population sample. The observed response of the
line in previous studies has been mixed. By focussing on extreme variability
($|\Delta g|>$ 1) we find that Mg II clearly does respond to the continuum.
However, the degree of responsiveness varies strikingly from one object to
another; we see cases of Mg II changing by as much as the continuum, more than
the continuum, or very little at all. In 74% of the highly variable sample the
behaviour of Mg II corresponds with that of H$\beta$, with 30% of the objects
showing large variations in both lines. We do not detect any change in the line
width that would correspond to Broad Line Region `breathing', in accordance
with results from literature. Some of the objects in our highly variable sample
show a clear asymmetry in the Mg II profile. This skewness can be both to the
blue and the red of the line centre. Results from our broad population sample
show that highly variable quasars have lower Eddington ratios. This result
holds for the variability of the continuum, but the correlation is
significantly reduced for the variability of the Mg II line. For the first
time, we present an overview of the value of the intrinsic Baldwin Effect for
Mg II in a large sample.
