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K. T. Lewis, M. Eracleous, R. M. Sambruna (Penn. State U.)
In recent surveys of Radio-loud AGN, a new sub-class of objects, known as Weak-Line Radio Galaxies (WLRGs) has emerged. These radio galaxies have only weak, low-ionization optical emission lines. In the X-ray band, these objects are much fainter and have flatter spectra than broad-line and narrow-line radio galaxies. In these respects, WLRGs are reminiscent of Low Ionization Nuclear Emission Regions (LINERs). We are carrying out a multi-wavelength study of WLRGs to better understand their possible connection to LINERs and the structure of the accretion flow in both these systems. Here, we present new optical spectra of a sample of WLRGs. We find that the majority of the objects have optical emission-line properties that are similar to LINERs, indicating that these two classes of AGN may be related. We also present the results of photoionization calculations aimed at interpreting the observed emission-line strength. These suggest that the enission-line gas in WLRGs has a very low ionization parameter, similar to what is seen in LINERs. The photoionization models also allow us to place indirect constraints on the shape of the Far Ultraviolet and soft X-ray continuum, which is extremely difficult to measure directly in these objects.