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Variability in the continuum and broad lines of Seyfert galaxies has been known for over 20 years. A number of Seyfert galaxies have been the subject of monitoring campaigns using both ground--based and space--based observatories. Since September, 1990, the Seyfert galaxy Markarian 509 has been observed with the Voyager , IUE, and ground--based observatories. We were able to cover Markarian 509 from 500--7000 \AA\ once a week for over two months. The Voyager spectrum extends from 500 to 1700 \AA\ with a resolution of $\sim$ 15 \AA. The IUE continuum was measured at 1350 \AA\ $\pm$ 20 \AA, 1840 \AA\ $\pm$ 20 \AA, and 2670 \AA\ $\pm$ 20 \AA, where these wavelengths are in the rest frame of Mrk 509. The flux in the Ly $\alpha\ \lambda$1216, C\,IV $\lambda$1549, and Mg\,II $\lambda$2798 emission lines were found by summing all the flux a ove the continuum in a certain interval. The optical continuum and H$\beta$\ measurements span a total of 1909 days, and the He$\lambda$4686 data cover 1671 days. The continuum and emission lines underwent large variations during the monitoring period, and that in general these variations were smooth and quite slow, at least in comparison to those seen in other well studied sources such as NGC~4151 The variations appear to be well resolved with our median sampling of 7 days. The lags measured for H$\beta$\ and He$\lambda$4686 are a factor or 3 -- 4 larger than lags that have been reliably measured for other AGNs, except in the case of the very luminous Seyfert~1 galaxy Fairall~9.
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