X-ray reflection from cold matter in the nuclei of active galaxies
Abstract
THE evidence accumulated over the past few years for strong soft X-ray emission from active galactic nuclei1-3 has been interpreted as black body emission from the innermost stable region of an accretion disk feeding the putative black hole at the centre of the active nucleus, a view given strong support by the rapid variability of some soft X-ray components4. More recently, new X-ray data from the Exosat and Ginga satellites have revealed a second indicator of optically thick matter in the vicinity of the active nucleus, in the form of an iron K-fluorescence line at ~6.4 keV (refs 5-8). We report the discovery of two further common features of continuum absorption and reflection, revealed in a composite spectrum from twelve Ginga observations of Seyfert-type active galactic nuclei. Most of these spectral features are shown to be well modelled by reprocessing of the hard X-ray power-law continuum in a slab (or perhaps a disk) of cold matter. There is also evidence for a substantial line-of-sight column of photoionized material.
- Publication:
-
Nature
- Pub Date:
- March 1990
- DOI:
- 10.1038/344132a0
- Bibcode:
- 1990Natur.344..132P
- Keywords:
-
- Active Galactic Nuclei;
- Cosmic X Rays;
- Dark Matter;
- K Lines;
- X Ray Sources;
- Fluorescence;
- Photoionization;
- Seyfert Galaxies;
- Astrophysics