The variable XMM-Newton spectrum of Markarian 766^*

¹ Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey, RH5 6NT, UK
² Instituto de Física de Cantabria (Consejo Superior de Investigaciones Científicas-Universidad de Cantabria), 39005 Santander, Spain
³ Science Operations Centre, Astrophysics Division, ESA Space Science Department, PO Box 50727, 28080 Madrid, Spain
⁴ Space Research Organization of The Netherlands, Laboratory for Space Research, Sorbonnelaan 2, Utrecht, CA 3584, The Netherlands
⁵ Astrophysikalisches Institut Potsdam, Sternwarte 16, 14482 Potsdam, Germany
⁶ NASA Goddard Space Flight Center, Code 660, Greenbelt, MD 20771, USA
⁷ X-Ray Astronomy Group, Department of Physics and Astronomy, Leicester University, Leicester LE1 7RH, UK
⁸ Los Alamos National Laboratory, NIS-2, Los Alamos, NM 87545, USA

Corresponding author: M. J. Page, mjp@mssl.ucl.ac.uk

Received: 2 October 2000
Accepted: 10 November 2000

Abstract

The narrow-line Seyfert 1 galaxy Mrk 766 was observed for 60 ks with the XMM-Newton 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 Kα 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. Mrk 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.