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Session 12 - Radio Galaxies, VLBI.
Display session, Monday, January 15
North Banquet Hall, Convention Center
The flat spectrum compact radio source PKS 1830-211 has been suggested to be a gravitational lens candidate based on the observed double structure of the source with a separation of 1 arcsec together with an elliptical ring-like structure connecting the two components. The redshifts of the radio source PKS 1830-211 and the lens have yet to be measured since searches in the optical and IR have failed to find a counterpart. \indent We present results from the analysis of an X-ray observation of PKS 1830-211 made with the ROSAT PSPC on 15 September 1993. In particular we investigated various emission and absorption mechanisms to describe the PSPC spectrum of PKS 1830-211. By fitting a simple ``absorbed power law'' to the PSPC pulse height distribution we find a hydrogen column density N_H of 6 x 10^20 atoms cm^-2 , which is in excess of that attributed to our galaxy. A model incorporating an absorbed power law with the hydrogen column density N_H fixed at the galactic value of 2.6 x 10^20 atoms cm^-2 plus an absorption edge also provided an acceptable \chi^2 fit to the spectrum with an energy index \alpha_E of 1.9 \pm 0.1 and an absorption edge at about 490 eV with an optical depth of 4.5. In both cases the results are suggestive that PKS 1830-211 is indeed extragalactic and strengthen the hypothesis that it is a gravitational lens system. More complex models produced by photoionization codes were used to fit the spectrum of PKS 1830-211 yielding information on the optical depth and the ionization state of the X-ray absorber.
