The XMM-Newton view of Mrk 3 and IXO 30

Abstract

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 Ka 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 × 1024 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 ≃0.82, suggested by the amount of reflection and the depth of the iron edge, are consistent with the iron Ka line equivalent width with respect to the Compton reflection component, which is 610-50+30 eV. Moreover, the iron linewidth, σ = 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 sin2 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 × 1022 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 Γ ≃ 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. © 2005 RAS.