XMM-Newton Observations of Luminous Narrow-Line Seyfert 1 Galaxies

We observed four optically-luminous narrow-line Seyfert 1 galaxies (NLS1s) with XMM-Newton. All the four NLS1s were detected. The observed X-ray spectra were rather steep (Γ= 2--3), as is typical among NLS1s. Utilizing simultaneous UV observations by the XMM-Newton optical monitor (OM), we also investigate the spectral energy distributions in the UV--X-ray band. One object (RX J1225.7+2055) of the four was found to be X-ray weak (α_ox∼2.0) during our observations. Compiling values of α_ox from a larger NLS1s, we find that, although the sample is small, the α_ox distribution suggests that X-ray weakness may occur more frequently among more luminous NLS1s.