Highly ionized Fe Kα emission lines from the LINER galaxy M 81

Abstract

We present spectral and timing results from a long (130 ks) XMM-Newton EPIC observation of the nucleus of the Seyfert/LINER galaxy M 81. During the observation the X-ray flux varied by 20%, but there was no significant change in spectral shape. The 2-10 keV spectrum is well described by a power law continuum and three narrow Fe Kα emission lines at 6.4, 6.7 and 6.96 keV. The three emission lines have equivalent widths of 39-12+13, 47-13+13 and 37-15+15 eV respectively. The ratios of the three lines are thus more similar to those observed from the Galactic Centre region than to those typically observed from Seyfert galaxies. The high ionization lines most likely originate either from photoionized gas within 0.1 pc of the nucleus of M 81, or from a non-thermal distribution of cosmic-ray electrons interacting with the 0.2-0.6 keV thermal plasma which is found in the bulge of M 81.