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A Composite HST Spectrum of Quasars

W. Zheng·G. A. Kriss·R. C. Telfer·J. P. Grimes·A. F. Davidsen
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Abstract

We construct a composite quasar spectrum from 284 HST FOS spectra of 101 quasars with redshifts z > 0.33. The spectrum covers the wavelengths between 350 and 3000 A in the rest frame. There is a significant steepening of the continuum slope around 1050 A. The continuum between 1050 and 2200 A can be modeled as a power law with alpha = -0.99. For the full sample the power-law index in the extreme ultraviolet (EUV) between 350 and 1050 A is alpha = -1.96. The continuum flux in the wavelengths near the Lyman limit shows a depression of about 10 percent. The break in the power-law index and the slight depression of the continuum near the Lyman limit are features expected in Comptonized accretion-disk spectra.

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W. Zheng, G. A. Kriss, R. C. Telfer, J. P. Grimes, A. F. Davidsen. 1996-08-29. A Composite HST Spectrum of Quasars. https://doi.org/10.1086/303560

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