XMM-Newton unveils the complex iron K alpha region of Mrk 279
  We present the results of a ~160 ks-long XMM-Newton observation of the
Seyfert 1 galaxy Mrk 279. The spectrum shows evidence of both broad and narrow
emission features. The Fe K alpha line may be equally well explained by a
single broad Gaussian (FWHM~10,000 km/s) or by two components: an unresolved
core plus a very broad profile (FWHM~14,000 km/s). For the first time we
quantified, via the "locally optimally emitting cloud" model, the contribution
of the broad line region (BLR) to the absolute luminosity of the broad
component of the Fe K alpha at 6.4 keV. We find that the contribution of the
BLR is only ~3%. In the two-line component scenario, we also evaluated the
contribution of the highly ionized gas component, which produces the FeXXVI
line in the iron K region. This contribution to the narrow core of the Fe K
alpha line is marginal <0.1%. Most of the luminosity of the unresolved,
component of Fe K alpha may come from the obscuring torus, while the very-broad
associated component may come from the accretion disk. However, models of
reflection by cold gas are difficult to test because of the limited energy
band. The FeXXVI line at 6.9 keV is consistent to be produced in a high column
density (N_H~10^23 cm^{-2}), extremely ionized (log\xi~5.5-7) gas. This gas may
be a highly ionized outer layer of the torus.
