Chandra Grating Spectroscopy of the Seyfert Galaxy Ton S180

Abstract

This paper presents results from spectral observations of Ton S180 using Chandra and ASCA. The data confirm the presence of the soft excess but the Chandra LETG spectrum reveals it to be broad and smooth, rather than resolved into individual emission lines. This excess may represent either a primary or reprocessed continuum component or a blend of broad lines from an ionized accretion disk. The occurrence of a similar feature in five other NLSy1s leads us to conclude that this soft X-ray component may be a characteristic of sources accreting at a very high rate. The X-ray spectrum shows no evidence for absorption lines, indicating that if gas exists in the line-of-sight then it is in a very high ionization-state or has an extremely broad velocity distribution. The new ASCA data confirm that the narrow component of the Fe Kalpha line peaks close to a rest-energy of 7 keV, indicating the presence of a significant amount of highly-ionized material in the nuclear environs.