A CONFIRMATION OF 2-40 KEV SPECTRAL COMPLEXITY IN SEYFERT-GALAXIES

We have reanalyzed 40 spectra of 25 Seyfert and narrow emission line g alaxies (NELGs) and one QSO, all of which were obtained during the poi nted observations phase (1978 May-1979 January) of the HEAO I A-2 expe riment. This investigation was prompted by Ginga results which indicat e that Fe Ka lines are common X-ray spectral features of active galact ic nuclei (AGNs) and that a high-energy ''bump'' associated with repro cessing of nuclear radiation may be common as well. The HEAO I data, w hich cover the 2-40 keV energy band, provide a large sample of AGNs wi th which to test the Ginga results. New analysis techniques are employ ed which consist of simultaneous fitting of data from both the medium- energy (2-20 keV) and high-energy (3-40 keV) detectors, as well as the subtracting of summed background spectra (up to 230,000 s of data) in order to improve the ratio of signal to noise. These improved techniq ues have resulted in the detection of Fe K features and/or spectral fl attening above similar to 5-10 keV in similar to 75% of the HEAO I sam ple. This confirms the Ginga result that spectral complexity is common in the X-ray spectra of Seyfert galaxies. We find that strong Fe K li nes tend not to be associated with the presence of high-energy flatten ing, implying that Fe Ka emission is not entirely the result of fluore scence from accretion disks. Our spectral results typically agree with Ginga for overlapping sources for which we have adequate signal-to-no ise ratios, although we find a significantly larger reflection compone nt in IC 4329A, NGC 5506, and Mrk 509. For IC 4329A and NGC 5506, a ti me lag in the response of the reflection component to variability in t he intrinsic source flux can explain the presence of more reflection, since the sources were fainter during the HEAO 1 epoch. A similar effe ct can explain the larger reflection component in Mrk 509, provided th e continuum underwent a flux outburst before or during HEAO 1 epoch.