Astronomy and Astrophysics – Astrophysics
Scientific paper
Oct 1987
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1987apj...321l..23w&link_type=abstract
Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X), vol. 321, Oct. 1, 1987, p. L23-L27.
Astronomy and Astrophysics
Astrophysics
45
Emission Spectra, Iron, Quasars, Visible Spectrum, X Ray Sources, Astronomical Models, Extragalactic Radio Sources, Spectrum Analysis, Ultraviolet Spectra
Scientific paper
Radio-quiet quasars generally show broad, blended multiplets of Fe II emission in their optical and UV spectra. Radio-loud quasars also show UV Fe II emission, but their optical Fe II emission is generally weaker. No satisfactory theory connecting the generation of Fe II and radio emission has been found to explain this effect. A second, well-established distinction between the two clases of quasar is in their X-ray properties: radio-loud quasars are more X-ray luminous, and recent results have shown that they also have systematically flatter soft X-ray slopes. Here it is proposed that the second effect causes the first; i.e., that the primary factor controlling the optical Fe II emission is the soft X-ray spectrum. This proposition is supported by X-ray and optical data for nine quasars, which shows a correlation between the soft X-ray slope and the strength of the optical Fe II emission. One of these quasars (1803+676) is radio-quiet, and yet its optical spectrum shows no evidence for Fe II emission. This quasar is also unusual in that it has a flat X-ray spectrum. This further supports the proposal that the X-ray spectrum is important in determining the relative strengths of UV and optical Fe II emission.
Elvis Martin
McHardy Ian
Wilkes Belinda J.
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