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J. R. Gabel, D. M. Crenshaw, S. B. Kraemer (Catholic University of America)
We present observations of the intrinsic UV absorption lines in the Seyfert 1 Galaxy NGC 3783 with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) and the Far Ultraviolet Spectroscopic Explorer (FUSE). The Lyman lines, C IV, N V, and O VI appear in four distinct kinematic components with radial velocities ranging between -500 and -1400 km s-1 with respect to the systemic velocity of the host galaxy. The high velocity gas, component 1, also shows absorption in Si IV, indicating that a relatively low ionization zone exists in this component. We have calculated photoionization models to match the measured column densities. Each component is characterized by a zone with high ionization parameter (U > 0.65) and a second, low ionization (U=0.0018) and low column density (4.9x1018 cm-2) zone is required for component 1. The O VIII column densities predicted by our models are smaller than the X-ray columns measured in Chandra spectra. We compare these STIS results with previous observations using the Goddard High Resolution Spectrograph (GHRS) and find no correlation between the UV absorbers and the UV continuum flux. This indicates that the variable strengths of the UV absorbers are due largely to changes in column densities as a result of transverse motion of the absorbing gas, rather than changes in the ionizing continuum.
The author(s) of this abstract have provided an email address for comments about the abstract: gabel@iacs.gsfc.nasa.gov