1997A&A...323..707E

In order to investigate the properties of the forbidden high-ionization lines (FHILs) in the spectra of AGN we observed 15 Seyfert galaxies and two emission line radio galaxies with a spectral resolution of about 2000 in the spectral range 3200-11000Å. All observed spectra contained significant [Ne V] and [Fe VII] lines. The spectra of the Seyfert nuclei (but not the radio galaxies) showed also [Fe X], [Fe XI], and in some cases [Fe XIV] emission. Our data confirm that the FHILs are on average broader and blueshifted relative to the lines of lower ionization stages. The amount of the blueshift was found to be correlated with the line widths. Large blueshifts were observed only for lines with high FWHM. An analysis of the line ratios indicates for the FHIL producing plasma an average electron temperature of about 7x10⁴K. Comparing our results with ROSAT data we found a correlation between the X-ray spectral index and the strength of the FHILs. Strong FHIL emission was found to occur predominantly in objects with a soft X-ray excess. We propose that the FHIL emission and the X-ray absorption edges in AGN ("warm absorbers") are related and that both phenomena result from a radiation driven warm wind originating in the central region of the AGN.