Active Galactic Nuclei
X-ray observations by EXOSAT shed new light on the compact
but intensely powerful sources at the heart of Active Galactic
Nuclei, such as the optically violent variable AGN ON 325
Prior to EXOSAT, AGN were not thought to show rapid variability. EXOSAT "long look" observations showed varibility down to timescales of ~ 1000 seconds.
This placed stringent constraints on the size of the emitting region, which could not be much larger than the inner solar system (~ 500 000 000 km).
The improved spectral resolution of the GSPC
compared to previous detectors led to
advances in the study of iron-emission features
in the spectra of many classes of object, such
as the AGN NGC1275
Last Update: 1 September 2019