X-ray spectra of active galaxies

Abstract

It is clear that x-ray spectroscopy has much to tell us about the nature of the active galactic nuclei phenomenon. In particular, with much more sensitivity and better spectral resolution devices available on future missions like BBXRT (a shuttle based x-ray spectrometer to fly in 1989), AXAF (the NASA Great Observatory for x-ray astronomy), XMM (the European Space Agency large multi-mirror x-ray mission scheduled to fly in 1998) and ASTRO-D (the Japanese x-ray spectroscopic mission scheduled to fly in 1993), we can anticipate that future observations will be quite interesting. In particular Fe line x-ray spectroscopy of AGN can be expected to strongly constrain models of the Broad Line Region in AGN. Continuum spectroscopy, in particular the determination of the nature of the ionizing continuum in the soft x-ray band, will be crucial in understanding these objects. I have neglected detailed discussion of the high energy, E>30 kev, continuum because of the paucity of data in this energy range. It is hoped that this band, which may contain the spectral signatures of the physics of the underlying energy generation mechanism, will be explored in more detail by future missions such as XTE (the U.S. X-ray Timing Explorer) and SAX (the Italian X-ray Astronomy saellite).