Chandra observations of nuclear X-ray emission from a sample of radio sources

¹ School of Computational Sciences, MS 5C3, George Mason University, 4400 University Drive, Fairfax, VA 22030, USA
² Department of Physics and Astronomy, MS 3F3, George Mason University, 4400 University Drive, Fairfax, VA 22030, USA
³ Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, State College, PA 16802, USA
⁴ Department of Physics, MS 057, Brandeis University, Waltham, MA 02454, USA
⁵ Osservatorio Astronomico di Brera, via Brera 28, Milan 20121, Italy
⁶ Department of Astronomy, PO Box 208101, Yale University, New Haven, CT 06520, USA

Corresponding author: J. K. Gambill, jessica@physics.gmu.edu

Received: 14 November 2002
Accepted: 30 January 2003

Abstract

We present the X-ray properties of a sample of 17 radio sources observed with the Chandra X-ray Observatory as part of a project aimed at studying the X-ray emission from their radio jets. In this paper, we concentrate on the X-ray properties of the unresolved cores. The sample includes 16 quasars (11 core-dominated and 5 lobe-dominated) in the redshift range –1.96, and one low-power radio-galaxy at . No diffuse X-ray emission is present around the cores of the quasars, except for the nearby low-power galaxy that has diffuse emission on a scale and with a luminosity consistent with other FRIs. No high-amplitude, short-term variability is detected within the relatively short Chandra exposures. However, 1510-089 shows low-amplitude flux changes with a timescale of ~25 min. The X-ray spectra of the quasar cores are generally well described by a single power law model with Galactic absorption. However, in six quasars we find soft X-ray excess emission below 1.6 keV. Interestingly, we detect an Fe K-shell emission line, consistent with fluorescent Kα emission from cold iron, in one lobe- and two core-dominated sources. The average X-ray photon index for the quasars in the sample is and dispersion . The average spectral slope for our sample is flatter than the slope found for radio-quiet quasars and for radio-loud AGNs with larger jet orientations; this indicates that beaming affects the X-ray emission from the cores in our sample of quasars.