A Statistical Analysis of the Broadband 0.1 to 3.5 keV Spectral Properties of X-Ray--selected Active Galactic Nuclei
Abstract
We survey the broadband spectral properties of ~500 X-ray-selected active galactic nuclei (AGNs) observed with the Einstein Observatory. Included in this survey are the ~450 AGNs in the Extended Medium Sensitivity Survey of Gioia et al. (1990) and the ~50 AGNs in the Ultrasoft Survey of Cordova et al. (1992). We present a revised version of the latter sample, based on the post publication discovery of a software error in the Einstein Rev-1b processing. We find that the mean spectral index of the AGNs between 0.1 and 0.6 keV is softer, and the distribution of indices wider, than previous estimates based on analyses of the X-ray spectra of optically selected AGNs. A subset of these AGNs exhibit flux variability, some on timescales as short as 0.05 days. A correlation between radio and hard X-ray luminosity is confirmed, but the data do not support a correlation between the radio and soft X-ray luminosities, or between radio loudness and soft X-ray spectral slope. Evidence for physically distinct soft and hard X-ray components is found, along with the possibility of a bias in previous optically selected samples toward selection of AGNs with flatter X-ray spectra.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 1994
- DOI:
- 10.1086/174704
- Bibcode:
- 1994ApJ...434...54T
- Keywords:
-
- Active Galactic Nuclei;
- Broadband;
- Radio Frequencies;
- Spectrum Analysis;
- Statistical Analysis;
- X Ray Spectra;
- Correlation;
- Heao 2;
- Mathematical Models;
- Sky Surveys (Astronomy);
- Stellar Luminosity;
- Astrophysics;
- GALAXIES: ACTIVE;
- X-RAYS: GALAXIES