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

• Published in: Monthly notices of the Royal Astronomical Society Vol. 436; no. 4; pp. 3173 - 3185
• Main Authors: Jin, Chichuan, Done, Chris, Middleton, Matthew, Ward, Martin
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 21-12-2013
• Subjects: Correlation analysis; Star & galaxy formation; X-ray astronomy
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stt1801

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. [PUBLICATION ABSTRACT]