Suzaku Wide-Band X-Ray Observation of the Narrow-Line Seyfert 1 Galaxy Ton S180

Abstract

We observed the luminous narrow-line Seyfert 1 galaxy Ton S180 with Suzaku, and obtained its wide-band (0.25-55 keV) X-ray spectra for the first time. The spectra were modeled with three components: a power-law component, a reflection from a highly ionized disk component, and an extra soft component either of a disk blackbody or a cutoff power-law. The reflection component accounts for the broad iron K line centered at 6.7 keV, and some fraction of the soft X-ray excess, including the O VIII line emission. The latter two components contribute comparably to the soft X-ray excess. When we adopt the disk blackbody model as the extra soft component, the disk inner radius temperature is 75 eV, much smaller than previously considered. This component is almost consistent with that expected for the slim-disk model assuming edge-on geometry. Hard X-ray emission above 15 keV was marginally detected. To account for the hard X-ray spectrum, we introduced Compton-thick partial absorbers. The absence of the neutral iron K line requires that those absorbers must be preferentially located along the line of sight. Fractional variability has little energy dependence below 10 keV, and is explained with a model in which the covering fraction of the Compton-thick absorber alters the observed flux.