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Hot dust on the outskirts of the broad-line region in Fairall 9
Clavel, J.; Wamsteker, W.; Glass, I. S.
AA(International Ultraviolet Explorer Observatory, Madrid, Spain), AB(International Ultraviolet Explorer Observatory, Madrid, Spain), AC(South African Astronomical Observatory, Observatory, Republic of South Africa)
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 337, Feb. 1, 1989, p. 236-250. (ApJ Homepage)
Publication Date:
NASA/STI Keywords:
Active Galactic Nuclei, Cosmic Dust, Infrared Sources (Astronomy), Seyfert Galaxies, Spectral Energy Distribution, Ultraviolet Spectra, Continuous Spectra, Light Curve, Line Spectra, Near Infrared Radiation
Bibliographic Code:


The Seyfert galaxy Fairall 9 (F9) has been observed in the far-UV and optical range with the IUE, and at 27 different epochs at J, H, K, and L. The UV continuum underwent dramatic variations, its intensity decreasing by a factor 33 from a maximum in 1978 to a deep minimum in mid-1984. The near-IR and optical fluxes changed by a factor of about three and in the same sense as the UV. The K and L emission are interpreted as thermal radiation from dust lying at about 1 lt-yr from the UV source. The Ly-alpha 1216, C IV 1550, and Mg II 2800 emission-line intensities also vary in the same sense as the UV continuum but with a lag of 155 + or - 45 days. This strongly suggests that the broad-line region (BLR) gas is photoionized and lies inside the dust shell. Strong evidence is presented that the Mg II 2800 line emissivity depends primarily on the density of soft X-ray photons, as postulated in optically thick photoionization models of the BLR.

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