Evidence for a multizone warm absorber in the XMM–Newton spectrum of Markarian 304

We present a XMM-Newton observation of Markarian 304, a Seyfert 1 galaxy at z = 0.066. The EPIC data show that MKN 304 is affected by heavy (N H 10 23 cm -2 ) obscuration arising from ionized gas. A two-phase warm absorber provides an adequate parametrization of this gas. The ionization parameter of the two components is ξ 6 erg cm -2 s -1 and ξ 90 erg cm -2 s -1 , respectively. The observed continuum photon index (r 1.9) is typical for Seyfert 1 galaxies. Two significant emission lines are detected at 0.57 keV and 6.4 keV, respectively. The former is mostly likely due to He-like oxygen triplet emission arising from an ionized plasma (maybe the warm absorber itself). The latter is due to fluorescent emission of K-shell iron in a low-ionization state (Fe i-xv). The upper limit for the line width of σ Kα < 0.18 keV most likely rules out an origin in the inner parts of the accretion disc. Interestingly, the strength of such line is consistent with the possibility that the emission is produced in the warm absorber itself. However, a substantial contribution from the torus is plausible too. We have also found a weak (4 per cent of the primary continuum) soft excess emission component. The presence of this excess could be explained by either emission/scattering from a warm gas or partial covering, or a combination of them.