Broadband nuclear emission in two radio-loud BAL quasars

Abstract

The X-ray weakness of broad absorption line (BAL) quasars in comparison to non-BAL objects is possibly caused by the absorption of X-ray emission by the shielding material near the equatorial plane. On the other hand, the radio-loud BALQSOs are more X-ray loud than the radio-quiet ones. This suggests that part of the X-ray emission may arise from the radio jet. To investigate this possibility, we modelled the nuclear spectra of two radio-loud BALQSOs. We focus on the emission from the very centres of these two objects. The source of emission was approximated by a single, homogeneous component that produces synchrotron and inverse-Compton (IC) radiation. The simplicity of the model allowed us to estimate the basic physical parameters of the emitting regions, using a universal analytic approach. Such methods have already been used in blazars. For the first time we propose this solution for quasars. In addition, we modelled the radiation spectra of the accretion disk and its corona to compare them with the jets' spectra. We find that in the case of luminous 3C270.1, the nuclear X-ray continuum is dominated by the non-thermal, IC emission from the innermost parts of the radio jet. However, the radio core of the lobe-dominated PG 1004+130 is probably too weak to produce significant part of the observed X-ray emission. A large contribution from the X-ray emitting accretion disk and corona is produced in our model. However, it then exceeds the observed flux. Because the large intrinsic absorption was postulated recently by the NuSTAR observations, we propose that the disk-corona component may still account for the X-rays produced in this source. This part of the spectrum must nevertheless be dominated by the X-ray jet. We conclude that the jet-linked X-ray emission is present in strong and weak radio sources, but its fraction seems to scale with the radio jet power.

10 pages, 6 figures. Accepted to Astronomy and Astrophysics. Online material (Appendix) will be available at A&A

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