  The discovery of an ultrafast outflow has been reported in the z=0.0658
narrow line Seyfert galaxy IRAS 13224-3809 (Parker et al. 2017a). The ultrafast
outflow was first inferred through the detection of highly blueshifted
absorption lines (Parker et al. 2017a) and then confirmed with a principal
component analysis (PCA) (Parker et al. 2017b). Two of the reported properties
of this outflow differed from those typically detected in other AGN with
ultrafast outflows. First, the outflow velocity was found not to vary with
v=0.236c +/- 0.006c. Second, the equivalent width of the highly blueshifted
absorption line was reported to be anti-correlated with the 3-10 keV flux of
this source. We present a re-analysis of the XMM-Newton observations of IRAS
13224-3809 considering the influence of background. We also undertook a
different analysis approach in combining the spectra and investigated the
change of the properties of the outflow as a function of 3-10 keV flux and
time. We confirm the presence of an ultrafast outflow in IRAS 13224-3809,
however, we find that the background spectra used in the Parker et al. analyses
dominate the source spectra for energies near the blueshifted iron lines. By
reducing the source extraction regions to improve the signal-to-noise ratio we
discover larger than previously reported outflow velocities and find that the
outflow velocity varies from ~0.2c to ~0.3c and increases with 3-10~keV flux.
The previously reported anti-correlation between equivalent width of the iron
line and 3-10 keV flux disappears when the background spectra are reduced by
optimizing the source extraction regions.
