A 100ks XMM-Newton view of the Seyfert 1.8 ESO113-G010. I. Discovery of large X-ray variability and study of the FeKalpha line complex

摘要

(Abridged) We present here a long (100ks) XMM-Newton follow-up of the Seyfert1.8 galaxy ESO113-G010 performed in November 2005, in order to study over alonger time-scale its main X-ray properties. The source was found in ahigher/softer time-averaged flux state, and timing analysis of this sourcereveals strong, rapid variability. The Power Spectral Density (PSD) analysisindicates (at 95% c.l.) a break at 3.7 x 10^-4 Hz. This cut-off frequency iscomparable to those measured in some other rapidly-variable Seyferts, such asMCG-6-30-15 and NGC4051. From the mass-luminosity-time-scale, we infer thatM_BH ranges from 4 x 10^6 - 10^7 M_odot and the source is accreting at or closeto the Eddington rate (or even higher). The existing data cannot distinguishbetween spectral pivoting of the continuum and a two-component origin for thespectral softening, primarily because the data do not span a broad enough fluxrange. In the case of the two-component model, the fractional offsets measuredin the flux-flux plots increase significantly toward higher energies (similarto what is observed in MCG-6-30-15) as expected if there exists a constantreflection component. Contrary to May 2001, no significant highly redshiftedemission line is observed (which might be related to the source flux level),while two narrow emission lines at about 6.5keV and 7keV are observed. The S/Nis not high enough to establish if the lines are variable or constant. Asalready suggested by the 2001 observation, no significant constant narrow6.4keV FeK line (EW~32eV) is observed, hence excluding any dominant emissionfrom distant cold matter such as a torus in this Seyfert type 1.8 galaxy.