On the origin of the X-rays and the nature of accretion in NGC 4261
George Mason University, Dept. of Physics & Astronomy & School of Computational Sciences, 4400 University Drive, MS 3F3, Fairfax, VA 22030, USA
2 The Pennsylvania State University, Department of Astronomy & Astrophysics, 525 Davey Lab, University Park, PA 16802, USA
Corresponding author: M. Gliozzi, email@example.com
Accepted: 7 July 2003
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 absorbed by a column density . The X-ray luminosity associated with the non-thermal component is . The nuclear source is embedded in a diffuse hot gas ( keV), whose density profile implies a Bondi accretion rate of . 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.
Key words: galaxies: active / galaxies: nuclei / X-rays: galaxies
© ESO, 2003