  XMM-Newton observed the Seyfert 1.9 galaxy NGC 4258 in December 2000. At
energies above 2 keV a hard nuclear point source is resolved that can be fitted
by a highly absorbed power-law spectrum (NH = (8.0+-0.4)x10^22 cm^-2, photon
index 1.64+-0.08) with an unabsorbed luminosity of 7.5x10^40erg/s in the 2-10
keV band. No narrow iron Kalpha emission line is detected (90% upper limit of
equivalent width EW ~40 eV). The nuclear emission flux was observed to remain
constant over the observation. A short archival Chandra observation taken in
March 2000 further constrains the hard emission to a point source coincident
with the radio nucleus. A point source ~3" southwest of the nucleus does not
contribute significantly. Spectral results of the Chandra nuclear source are
comparable (within the limited statistics) to the XMM-Newton parameters. The
comparison of our iron line upper limit with reported detections indicates
variability of the line EW. These results can be explained by the relatively
low nuclear absorption of NGC 4258 (which is in the range expected for its
intermediate Seyfert type) and some variability of the absorbing material.
Reflection components as proposed to explain the large iron line EW of highly
absorbed Seyfert 2 galaxies and/or variations in the accretion disk are however
imposed by the time variability of the iron line flux.
