Spectral and time series analyses of the Seyfert 1 AGN: Zw 229.015

Abstract

We analyse the spectra of the archival XMM–Newton data of the Seyfert 1 AGN Zw 229.015 in the energy range 0.3–10.0 keV. When fitted with a simple power law, the spectrum shows signatures of weak soft excess below 1.0 keV. We find that both thermal Comptonization and relativistically blurred reflection models provide the most acceptable spectral fits with plausible physical explanations to the origin of the soft excess than do multicolour disc blackbody and smeared wind absorption models. This motivated us to study the variability properties of the soft and the hard X-ray emissions from the source and the relationship between them to put further constraints on the above models. Our analysis reveals that the variation in the 3.0–10.0 keV band lags that in the 0.3–1.0 keV by |${600^{+290}_{-280}}\,\mathrm{s}$|⁠, while the lag between the 1.0-10.0 keV and 0.3–1.0 keV is |${980^{+500}_{-500}}\,\mathrm{s}$|⁠. This implies that the X-ray emissions are possibly emanating from different regions within the system. From these values, we estimate the X-ray emission region to be within 20Rg of the central supermassive black hole (where Rg = GM/c2, M is the mass of black hole, G Newton's gravitational constant and c the speed of light). Furthermore, we use XMM–Newton and Kepler photometric light curves of the source to search for possible non-linear signature in the flux variability. We find evidence that the variability in the system may be dominated by stochasticity rather than deterministic chaos which has implications for the dynamics of the accretion system.