  An analysis was made of 0.3-15 keV X-ray spectra of a Narrow-Line Seyfert 1
Galaxy, Ton S180, using archival data from ASCA, RXTE, and XMM-Newton. At
energies above 2.5 keV, a power-law with a photon index of ~ 2.3 successfully
and consistently reproduced the spectra from all of these observatories.
Assuming this power-law component to extend toward lower energies, a soft
excess, which is one of the most remarkable features of Narrow-Line Seyfert 1
Galaxies, is explained by another power-law multiplied by a thermal cutoff at ~
0.4 keV. Some similarities have been observed between this object and Galactic
black hole binaries in very high state, the latter being realized under high
accretion rates. Attempts have been made to interpret the soft excess in terms
of Comptonization of the disk photons by an electron cloud surrounding the
accretion disk, like BHBs in a very high state.
