We analyze X-ray spectra of 43 Palomar-Green quasars observed with XMM-Newton in order to investigate their mean Fe K line profile and its dependence on physical properties .
The continuum spectra of 39 objects are well reproduced by a model consisting of a power law and a blackbody modified by Galactic absorption .
The spectra of the remaining four objects require an additional power-law component absorbed with a column density of \sim 10 ^ { 23 } { cm } ^ { -2 } .
A feature resembling an emission line at 6.4 keV , identified with an Fe K line , is detected in 33 objects .
Approximately half of the sample show an absorption feature around 0.65–0.95 keV , which is due to absorption lines and edges of O vii and O viii .
We fit the entire sample simultaneously to derive average Fe line parameters by assuming a common Fe line shape .
The Fe line is relatively narrow ( \sigma = 0.36 keV ) , with a center energy of 6.48 keV and a mean equivalent width ( EW ) of 248 eV .
By combining black hole masses estimated from the virial method and bolometric luminosities derived from full spectral energy distributions , we examine the dependence of the Fe K line profile on Eddington ratio .
As the Eddington ratio increases , the line becomes systematically stronger ( EW = 130 to 280 eV ) , broader ( \sigma = 0.1 to 0.7 keV ) , and peaks at higher energies ( 6.4 to 6.8 keV ) .
This result suggests that the accretion rate onto the black hole directly influences the geometrical structure and ionization state of the accretion disk .
We also examine a two-component model consisting of a Gaussian and a diskline to constrain the intensity of the broad line .
The mean equivalent widths are \approx 70 - 180 eV for the four Eddington ratio groups , although the standard deviations in each group are very large .
This suggests that the broad line is not ubiquitous .