X-ray selected Narrow-Line Seyfert 1 Galaxies
  We present and discuss the properties of a complete and well defined sample of X-ray selected type 1 AGNs including 26 Narrow-Line Seyfert 1 and 129 Broad-Line Seyfert 1 galaxies derived from the XMM-Newton Bright Serendipitous Survey (XBS). We study the differences between the two classes of AGNs for what concerns the X-ray properties (the photon-index) and the main physical parameters, like the Black-Hole mass and the Eddington ratio. We then consider the two classes together and look for statistical correlations between observed and physical parameters. We find a significant dependence of the photon-index with the Eddington ratio and a weaker (possibly secondary) correlation between the photon index and the Black-Hole Mass. 
A. Caccianiga, P. Severgnini, R. Della Ceca, A. Corral, R. Fanali, E.   Marchese
astro-ph.CO