2013MNRAS.436.3173J

We explore the origin of the strong soft X-ray excess in narrow-line Seyfert 1 galaxies using spectral-timing information from a 120ks XMM-Newton observation of PG 1244+026. Spectral fitting alone cannot distinguish between a true additional soft X-ray continuum component and strongly relativistically smeared reflection, but both models also require a separate soft blackbody component. This is most likely intrinsic emission from the disc extending into the lowest energy X-ray bandpass. The rms spectra on short time-scales (200-5000s) contain both (non-disc) soft excess and power-law emission. However, the spectrum of the variability on these time-scales correlated with the 4-10keV light curve contains only the power law. Together these show that there is fast variability of the soft excess which is independent of the 4-10keV variability. This is inconsistent with a single reflection component making the soft X-ray excess as this necessarily produces correlated variability in the 4-10keV bandpass. Instead, the rms and covariance spectra are consistent with an additional cool Comptonization component which does not contribute to the spectrum above 2keV.