We present simultaneous XMM- Newton and NuSTAR observations of the ‘ bare ’ Seyfert 1 galaxy , Ark 120 , a system in which ionized absorption is absent .
The NuSTAR hard X-ray spectral coverage allows us to constrain different models for the excess soft X-ray emission .
Among phenomenological models , a cutoff power law best explains the soft X-ray emission .
This model likely corresponds to Comptonization of the accretion disk seed UV photons by a population of warm electrons : using Comptonization models , a temperature of \sim 0.3 keV and an optical depth of \sim 13 are found .
If the UV-to-X-ray optxagnf model is applied , the UV fluxes from the XMM- Newton Optical Monitor suggest an intermediate black hole spin .
Contrary to several other sources observed by NuSTAR , no high energy cutoff is detected , with a lower limit of 190 keV .