The variable XMM-Newton spectrum of Markarian 766

The narrow-line Seyfert 1 galaxy Markarian 766 was observed for 60 ks with the \xmm\ observatory. The source shows a complex X-ray spectrum. The 2-10 keV spectrum can be adequately represented by a power law and broad Fe Kalpha emission. Between 0.7 and 2 keV the spectrum is harder and exhibits a flux deficit with respect to the extrapolated medium energy slope. Below 0.7 keV, however, there is a strong excess of emission. The RGS spectrum shows an edge-like feature at 0.7 keV; the energy of this feature is inconsistent with that expected for an OVII edge from a warm absorber. Markarian 766 varies by a factor of ~ 2 in overall count rate in the EPIC and RGS instruments on a timescale of a few thousand seconds, while no significant flux changes are observed in the ultraviolet with the OM. The X-ray variability is spectrally dependent with the largest amplitude variability occurring in the 0.4-2 keV band. The spectral variability can be explained by a change in flux and slope of the medium energy continuum emission, superimposed on a less variable (or constant) low energy emission component. Based on observations obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).