The HUT Spectrum of Fairall 9

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Session 20 -- Astro 2
Display presentation, Tuesday, June 13, 1995, 9:20am - 6:30pm

[20.01] The HUT Spectrum of Fairall 9

W. Zheng, G. A. Kriss, A. F. Davidsen, and J. W. Kruk (JHU)

We observed the Seyfert galaxy Fairall 9 with the Hopkins Ultraviolet Telescope (HUT) during the Astro-2 mission for $\sim 3800$s. The far-UV continuum is unattenuated to wavelengths as short as 920 \AA\ ($\sim 880$~\AA\ in the galaxy's rest frame) and can be fitted with a power law of $\alpha \approx -1.3\ (f_\nu \propto \nu^\alpha)$, a value close to that derived from the IUE spectra.

The intensity of O{\sc vi} $\lambda\lambda$1031,1037+Ly$\beta$ emission is $\sim 0.35$ times that of the C{\sc iv} $\lambda$ 1549 line. The ratio between these two emission features is one of the lowest among the AGNs observed by HUT. The He{\sc ii} $\lambda$1640/Ly$\alpha$ ratio is $\sim 0.03$.

The power-law fit to the far-UV continuum of Fairall 9 may be extrapolated to connect to the soft X-ray component measured by ROSAT and Ginga, forming a moderate UV Bump. Photoionization by a source of such an energy distribution would produce relatively weak high-ionization lines as observed.

This work is supported by NASA contract NAS 5-27000 to the Johns Hopkins University.

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