The warm absorber and X-ray variability of the Seyfert 1 galaxy NGC 3516
  as seen by the XMM-Newton RGS
  We present a new analysis of the soft and medium energy X-ray spectrum of the
Seyfert 1 galaxy NGC 3516 taken with the Reflection Grating Spectrometer (RGS)
and European Photon Imaging Camera (EPIC) on board the XMM-Newton observatory.
We examine four observations made in October 2006. We investigate whether the
observed variability is due to absorption by the warm absorber and/or is
intrinsic to the source emission. We analyse in detail the EPIC-pn and RGS
spectra of each observation separately. The warm absorber in NGC 3516 is found
to consist of three phases of ionisation, two of which have outflow velocities
of more than 1000 km/s. The third phase (the least ionised one) is much slower
at 100 km/s. One of the high ionisation phases, with log xi of 2.4, is found to
have a partial covering fraction of about 60%. It has previously been suggested
that the passage of a cloud, part of a disk wind, in front of the source
(producing a change in the covering fraction) was the cause of a significant
dip in the lightcurve during one of the observations. From our modelling of the
EPIC-pn and RGS spectra, we find that variation in the covering fraction cannot
be solely responsible for this. We show that intrinsic change in the source
continuum plays a much more significant role in explaining the observed flux
and spectral variability than originally thought.
