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Session 50 - Active Galaxies.
Display session, Tuesday, January 16
North Banquet Hall, Convention Center

[50.09] ROSAT Observations of Narrow-Line Type 1 Seyfert Galaxies.

K. Forster (Columbia U.)

ROSAT PSPC spectra of a sample of optically-selected narrow-line type 1 Seyfert galaxies have been studied and the results are compared to their optical, infrared and radio properties in an attempt to interpret the strong Fe \tenrm II emission and steep x-ray spectra prevalent in this class of AGN. The selection by optical emission lines avoids any bias in x-ray spectral properties that might be induced by soft x-ray selection. The observed soft x-ray spectra are well characterized by a power law of large mean photon index, \langle\Gamma\rangle = 2.99, with a dispersion of 0.61 (very similar to that found by Boller, Brandt, amp; Fink 1995). A highly significant correlation between \Gamma and the 0.1 -- 2.0 keV luminosity exists in this sample; higher luminosity objects have softer spectra. This is reminiscent of the behavior of the x-ray spectra of Galactic black hole candidates. However, no evidence is found for any consistent spectral changes during x-ray variability in individual objects in the sample.

The characteristics of the narrow-line sample were compared to those of a control sample of 103 AGN of all classes observed with ROSAT. A K-S test was performed on these two samples and it was found that:

1) The narrow-line sample has a significantly different distribution of \Gamma than the control sample which has a mean photon index \langle\Gamma\rangle = 2.36, with a dispersion of 0.43.

2) The flux ratio Fe \tenrm II/H\beta is significantly higher in the narrow-line sample than in the control sample even though the distribution of the equivalent width of Fe \tenrm II is the same.

3) The narrow-line objects have the same distribution of x-ray, optical, far infrared, and radio luminosities as the control sample.

Program listing for Tuesday