X-Ray Properties of the Quasar HE 0450-2958

We present an {\it XMM-Newton} EPIC observation of HE0450-2958 which may be a``naked''quasar as suggested by Magain et al. The \xmm EPIC spectra show asubstantial soft X-ray excess, a steep photon index, as well as marginalevidence for a weak Fe K$\alpha$ line. The X-ray absorption is consistent withthe galactic level. The 0.3-10 keV EPIC spectra can be fitted by a power lawplus a blackbody model, however, the fit by the relativistically blurredphotoionized disc reflection is better. We estimate the black hole mass of$2^{+7}_{-1.3} \times 10^{7} M_{\odot}$ from the X-ray variability. Thisbroadly agrees with the value derived from the optical \hb line width. Theseresults support a high-state Seyfert galaxy of the source. HE0450-2958 sharessimilar properties of transitionary objects from ultra-luminous infraredgalaxies to quasars. We suggest that HE0450-2958 is just in the beginning of anoptical quasar window.Comment: 23 pages, 8 figures, AJ in pres