Bensch, K.K.Benschdel Olmo, A.A.del OlmoSulentic, J.J.SulenticPerea, J.J.PereaMARZIANI, PaolaPaolaMARZIANI2020-04-232020-04-2320150250-6335http://hdl.handle.net/20.500.12386/24204We present a preliminary analysis of X-ray data of quasars in the context of the 4D eigenvector 1 parameter space (Sulentic et al. 2000a, b). 4DE1 serves as a surrogate H-R diagram for representing empirical diversity among quasars and identifying the physical drivers of the diversity. The soft X-ray spectral index (Γ<SUB>soft</SUB>) was adopted as one of the key 4DE1 that correlates contrasting extremes in Type 1 properties. 4DE1 motivated the hypothesis of two quasar populations (A and B) divided by L/ L <SUB>EDD</SUB>≈0.2. Pop. A is a largely radio-quiet population with FWHM H β<4000 km/s and often showing a soft X-ray excess. Pop. B is a mix of radio-quiet and a majority of RL quasars shows only a hard X-ray power-law SED. The X-ray separation was based upon earlier ROSAT and ASCA data but we now confirm this dichotomy with large samples of X-ray spectra obtained with XMM-Newton and SWIFT. One popular idea connects the soft excess in Pop. A quasars as a signature of thermal emission from a hot accretion disk in sources radiating close to the Eddington limit. <P />STAMPAenArticle10.1007/s12036-015-9355-82-s2.0-84956844290000368698700006https://link.springer.com/article/10.1007%2Fs12036-015-9355-82015JApA...36..467BFIS/05 - ASTRONOMIA E ASTROFISICA