On the origin of the X-rays and the nature of accretion in NGC 4261

Free access article

Issue		A&A Volume 408, Number 3, September IV 2003


Page(s)		949 - 959
Section		Galactic structure and dynamics
DOI		http://dx.doi.org/10.1051/0004-6361:20031050

A&A 408, 949-959 (2003)
DOI: 10.1051/0004-6361:20031050

On the origin of the X-rays and the nature of accretion in NGC 4261

M. Gliozzi¹, R. M. Sambruna¹ and W. N. Brandt²

¹ 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

(Received 11 April 2003 / Accepted 7 July 2003)

Abstract
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 $N_{\rm H}> 5\times 10^{22}{~\rm cm^{-2}}$ . The X-ray luminosity associated with the non-thermal component is ${\sim} 5 \times 10^{41} {~\rm erg~s^{-1}}$ . The nuclear source is embedded in a diffuse hot gas ( $kT\sim0.6{-}0.65$ keV), whose density profile implies a Bondi accretion rate of ${\sim} 4.5\times 10^{-2}{~ M_\odot\rm ~ yr^{-1}}$ . 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.

Key words: galaxies: active -- galaxies: nuclei -- X-rays: galaxies

Offprint request: M. Gliozzi, mario@physics.gmu.edu

SIMBAD Objects

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.