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publication

X-ray spectra of two quasars at z>1

K. Nandra, A.C. Fabian, W.N. Brandt, H. Kunieda, M. Matsuoka, T. Mihara, Y. Ogasaka, and Y. Terashima
Abstract

We present the ASCA spectra of PG 1634+706 (z=1.334) and PG 1718+481 (z=1.084). The most striking result of our analysis is that no `reflection features' - an Fe Kalpha emission line and `hard tail' - have been detected in the spectra. This contrasts markedly with the case of Seyfert galaxies, where such features are almost universal. This immediately excludes X-ray reprocessing as an origin for the (extremely luminous) blue bumps in these sources. The lack of these features is rather puzzling. In the absence of substantial X-ray beaming, we conclude that the accretion disc in these objects is either very highly ionized or optically thin. Either case might indicate that the sources are emitting close to the Eddington limit, which should cause the inner disc to expand. Furthermore, any optically thick, molecular torus, like that hypothesized in some Seyfert unification schemes, either is absent or subtends a small solid angle at the X-ray source.

 
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