EXOSAT OBSERVATIONS OF THE BLAZAR PKS 1510-089

A detailed study of X-ray emission from the high-polarization quasar PKS 1510-089, also known as a blazar, is presented, based on the EXOSAT observations in 1984 and 1985. The data were obtained from the EXOSAT archives. There is no evidence for any variations in the X-ray intensity on hourly time scales during either of the two observations. The 2-10 keV X-ray flux shows no significant change over a year. The observed X-ray spectral data is best fitted by a power law with a photon index, Γ, of 1.40-0.30+0.35 (error bars are with 90% confidence). The slope of the power law is somewhat flatter for PKS 1510-089 as compared with the canonical spectra of the active galactic nuclei; however, the present observations do not rule out a normal Seyferttype spectrum. There is no detection of any significant low-energy absorption within the blazar, nor is there any evidence for a soft X-ray excess. A line feature modeled as a Gaussian is detected with a high significance near 5 keV. The emission line could be the redshifted 6.4 keV line due to the fluorescence of cold iron present around the nucleus of PKS 1510-089 or the redshifted 6.7 keV line due to ionized iron in a hot plasma. The observed intensity of the line, if produced by fluorescence, would require the cold matter to subtend a very large solid angle to the X-ray continuum source.