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 100–150 keV is well described by a partially covered ( covering factor > 0.8 ) power law with a photon index \Gamma \simeq 1.5 absorbed by a column density N _ { H } > 5 \times 10 ^ { 22 } { ~ { } cm ^ { -2 } } .
The X-ray luminosity associated with the non-thermal component is \sim 5 \times 10 ^ { 41 } { ~ { } erg~ { } s ^ { -1 } } .
The nuclear source is embedded in a diffuse hot gas ( kT \sim 0.6 - 0.65 keV ) , whose density profile implies a Bondi accretion rate of \sim 4.5 \times 10 ^ { -2 } { ~ { } M _ { \odot } ~ { } yr ^ { -1 } } .
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 .