Current issues in the X-ray properties of active galactic nuclei.
Abstract
Some issues raised by soft X-ray spectra and hours variability observations of active galactic nuclei (AGN), made possible by improved energy calibration of the Einstein IPC and the launch of Exosat into a unique 72-hour highly elliptical orbit, are presented. Explanations for steep soft excesses in quasars include the emission from the hot tail of an accretion disk spectrum, and from optically thin bremsstrahlung at 1-2 x 10 to the 6th K from a large volume. Mechanisms for the approximately 1.0 slope in the 0.2-4 keV soft IPC X-ray band quasars include direct synchrotron emission, unsaturated Comptonization of an arbitrary seed spectrum, and synchro-Compton scattering from the infrared. The Exosat observation of NGC 4051 revealed six 1-hour cycles with spectral changes during the variations. AGN time variations may now be able to limit emission models through studying, for example, the lag times between soft and hard variations.
- Publication:
-
Publications of the Astronomical Society of the Pacific
- Pub Date:
- February 1986
- DOI:
- 10.1086/131736
- Bibcode:
- 1986PASP...98..148E
- Keywords:
-
- Active Galactic Nuclei;
- Quasars;
- X Ray Astronomy;
- Compton Effect;
- Exosat Satellite;
- Seyfert Galaxies;
- Spectrum Analysis;
- X Ray Spectra;
- Astrophysics