Probing the complex and variable X-ray absorption of Markarian 6 with XMM-Newton

We report on an X-ray observation of the Seyfert 1.5 galaxy Mrk 6 obtained with the EPIC instruments on board XMM-Newton. Archival BeppoSAX Phoswich Detection System data from 18-120 keV were also used to constrain the underlying hard power-law continuum. The results from our spectral analyses generally favor a double partial-covering model, although other spectral models, such as absorption by a mixture of partially ionized and neutral gas, cannot be firmly ruled out. Our best-fitting model consists of a power law with a photon index of Γ = 1.81_-0.20^+0.22 and partial covering with large column densities up to N_H ∼ 10²³ cm^-2. We also detect a narrow emission line consistent with Fe Kα fluorescence at 6.45_-0.04^+0.03 keV with an equivalent width of 93_-20^-26 eV. Joint analyses of XMM-Newton, ASCA, and BeppoSAX data further provide evidence for both spectral variability (a factor of ∼2 change in absorbing column) and absorption-corrected flux variations (by ∼60%) during the ∼4 yr period probed by the observations.