Warm absorber and truncated accretion disc in IRAS 05078+1626
  X-ray observations of unabsorbed active galactic nuclei provide an
opportunity to explore the innermost regions of supermassive black hole
accretion discs. Our goal in this paper is to investigate the central
environment of a Seyfert 1.5 galaxy IRAS 05078+1626. We studied the
time-averaged spectrum obtained with the EPIC and RGS instruments. A power-law
continuum (photon index ~ 1.75) dominates the 2-10 keV energy range. A narrow
iron K alpha spectral line is clearly seen, presumably originating in a distant
torus, but no broad relativistic component was detected. However, the power law
and the iron K alpha line alone do not provide a satisfactory fit in the soft
X-ray band whose spectrum can be explained by the combination of three
components: a) a cold photoelectric absorber with column density ~ 10^(21)
cm^(-2). This gas could be located either in outer parts of the accretion disc,
at the rim of the torus or farther out in the host galaxy; b) a warm absorber
with high ionization parameter (log(xi) ~ 2.2) and column density ~ 10^(24)
cm^(-2); c) an ionized reflection where the reflecting gas could be either in
the inner wall of a warm absorber cone or in an ionized accretion disc. The
first X-ray spectroscopic measurement of IRAS05078+1626 unveils some of the
standard ingredients in Seyfert galaxies, such as a power-law primary
continuum, modified by reflection from the accretion disc and by the effect of
complex, multi-phase obscuration. However, data constrains the accretion disc,
if present, not to extend closer than to 60 gravitational radii from the black
hole.
