Current issues in the X-ray properties of active galactic nuclei

Journal Article · Sat Feb 01 04:00:00 EST 1986 · Publ. Astron. Soc. Pac.; (United States)

DOI:https://doi.org/10.1086/131736· OSTI ID:5454819

Elvis, M

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. 47 references.

• Research Organization: Harvard-Smithsonian Center for Astrophysics, Cambridge, MA
• OSTI ID: 5454819
• Journal Information: Publ. Astron. Soc. Pac.; (United States), Journal Name: Publ. Astron. Soc. Pac.; (United States) Vol. 98; ISSN PASPA
• Country of Publication: United States
• Language: English

Related Subjects

640103* -- Astrophysics & Cosmology-- Quasi-Stellar
Radio
& X-Ray Sources-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCRETION DISKS
BASIC INTERACTIONS
COMPTON EFFECT
COSMIC RADIO SOURCES
ELASTIC SCATTERING
ELECTROMAGNETIC INTERACTIONS
GALAXIES
GALAXY NUCLEI
INTERACTIONS
QUASARS
SCATTERING
SEYFERT GALAXIES
SPECTRA
VARIATIONS
X-RAY SPECTRA