A long XMM-Newton observation of an extreme narrow-line Seyfert 1 : PG 1244+026.

We explore the origin of the strong soft X-ray excess in narrow-line Seyfert 1 galaxies using spectral-timing information from a 120 ks 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 (200–5000 s) contain both (non-disc) soft excess and power-law emission. However, the spectrum of the variability on these time-scales correlated with the 4–10 keV light curve contains only the power law. Together these show that there is fast variability of the soft excess which is independent of the 4–10 keV variability. This is inconsistent with a single reflection component making the soft X-ray excess as this necessarily produces correlated variability in the 4–10 keV bandpass. Instead, the rms and covariance spectra are consistent with an additional cool Comptonization component which does not contribute to the spectrum above 2 keV