2003A&A...408..949G

We report on the X-ray properties of the radio galaxy NGC 4261, combining information from the XMM-Newton, Chandra, and BeppoSAX satellites. Goals of this study are to investigate the origin of the X-rays from this low-power radio galaxy and the nature of the accretion process onto the central black hole. The X-ray spectrum of the nuclear source extending up to 100-150keV is well described by a partially covered (covering factor >0.8) power law with a photon index Γ≃1.5 absorbed by a column density N_H>5x10²²cm^–2. The X-ray luminosity associated with the non-thermal component is ∼5x10⁴¹erg/s. The nuclear source is embedded in a diffuse hot gas (kT∼0.6-0.65keV), whose density profile implies a Bondi accretion rate of ∼4.5x10^–2M_☉/yr. For the first time rapid X-ray variability is detected in a low-power radio galaxy at more than 99% confidence level. The observed X-ray spectral and variability properties indicate the accretion flow as the most likely origin of the bulk X-ray continuum. This conclusion is strengthened by energetic considerations based on a comparison between the X-ray luminosity and the kinetic power of the jet, which also suggest that the Bondi accretion rate overestimates the actual accretion rate onto the black hole.