Survey of Bare Active Galactic Nuclei in the Local Universe (z < 0.2). I. On the Origin of Soft Excess

Abstract

We analyze a sample of 21 "bare" Seyfert 1 active galactic nuclei, a subclass of Seyfert 1 galaxies, with intrinsic absorption N _H ~ 10²⁰ cm^-2, in the local Universe (z < 0.2) using XMM-Newton and Swift/XRT observations. The luminosities of the primary continuum, the X-ray emission in the 3-10 keV energy range, and the soft excess-the excess emission that appears above the low-energy extrapolation of the power-law fit of 3-10 keV X-ray spectra-are calculated. Our spectral analysis reveals that the long-term intrinsic luminosities of the soft excess and the primary continuum are tightly correlated $({L}_{\mathrm{PC}}\propto {L}_{\mathrm{SE}}^{1.1\pm 0.04})$ . We also found that the luminosities are correlated for each source. This result suggests that both the primary continuum and soft excess emissions exhibit a dependency on the accretion rate in a similar way.