The XMM-Newton view of Mrk 3 and IXO 30

We present the analysis of the XMM-Newton European Photon Imaging Camera (EPIC) pn spectrum of the Seyfert 2 galaxy Mrk 3. We confirm that the source is dominated by a pure Compton reflection component and an iron K alpha line, both produced as a reflection from a Compton-thick torus, likely responsible also for the large column density (1.36(-0.04)(+0.03) x 10(24) cm(-2)) which is pierced by the primary power law only at high energies. A low inclination angle and an iron underabundance of a factor similar or equal to 0.82, suggested by the amount of reflection and the depth of the iron edge, are consistent with the iron K alpha line equivalent width with respect to the Compton reflection component, which is 610(-50)(+30) eV. Moreover, the iron linewidth, sigma = 32(-14)(+13) eV, if interpreted in terms of Doppler broadening due to the Keplerian rotation of the torus, puts an estimate to the inner radius of the latter, r = 0.6(-0.3)(+1.3) sin(2) i pc. Finally, two different photoionized reflectors are needed to take into account a large number of soft X-ray emission lines from N, O, Ne, Mg, Si, Fe L and the Fe xxv emission line at 6.71(-0.02)(+0.03) keV. RGS spectra show that the soft X-ray spectrum is dominated by emission lines, while the underlying continuum is best fitted by an unabsorbed power law with the same photon index as the primary continuum, produced as a reflection by a photoionized material with a column density of a few x 10(22) cm(-2). We also present the first X-ray spectrum of the ROSAT source IXO 30, which shows a huge iron line at 6.5(-0.2)(+0.3) keV and is well represented either by an absorbed power law with Gamma similar or equal to 1.8 or by bremsstrahlung emission at a temperature of 7.5(-1.6)(+2.1) keV. Its spectral properties point to a likely identification in terms of a weak Galactic cataclysmic variable, but the lack of any optical counterpart precludes excluding other possibilities, such as an ultraluminous X-ray source at the distance of Mrk 3.