Results 31 to 40 of about 274,748 (260)
Rapid X-Ray Variability in Active Galactic Nuclei [PDF]
Symposium - International Astronomical Union, 1986 SummaryRecent EXOSAT observations of active galactic nuclei are presented. Unlike earlier X-ray satellites (all of which flew in low earth orbit), the deep orbit of EXOSAT allows long continuous observations of celestial X-ray sources, uninterrupted by earth occultation etc.
J. Clavel +4 more
openaire +2 more sources
X-Ray Unveiling Events in a z ≈ 1.6 Active Galactic Nucleus in the 7 Ms Chandra Deep Field-South
The Astrophysical Journal, 2023 We investigate the extreme X-ray variability of a z = 1.608 active galactic nucleus in the 7 Ms Chandra Deep Field-South (XID 403), which showed two significant X-ray brightening events.
Li-Ming Yu +16 more
doaj +1 more source
The Astrophysical Journal Letters, 2023 Recent studies have proposed that the nuclear millimeter continuum emission observed in nearby active galactic nuclei (AGNs) could be created by the same population of electrons that gives rise to the X-ray emission that is ubiquitously observed in ...
Claudio Ricci +12 more
doaj +1 more source
X-Rays from Active Galactic Nuclei [PDF]
Highlights of Astronomy, 1983 Recent X-ray observations of active galactic nuclei and Seyfert galaxies in particular are briefly reviewed. The application of the efficiency limit to rapidly varying luminous sources such as NGC 6814 is discussed. It is argued that the variability and probable MeV spectral turnover imply that most of the electrons which radiate the observed flux are ...
openaire +2 more sources
, 2009 TANAMI (Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry) is a monitoring program to study the parsec-scale structures and dynamics of relativistic jets in active galactic nuclei (AGN) of the Southern Hemisphere with the Long ...
Boeck, M. +25 more
core +2 more sources
Unwrapping the X‐ray spectra of active galactic nuclei [PDF]
Astronomische Nachrichten, 2016 AbstractActive galactic nuclei (AGN) are complex phenomena. At the heart of an AGN is a relativistic accretion disk around a spinning supermassive black hole (SMBH) with an X‐ray emitting corona and, sometimes, a relativistic jet. On larger scales, the outer accretion disk and molecular torus act as the reservoirs of gas for the continuing AGN activity.
openaire +6 more sources
A High Fraction of Heavily X-Ray-obscured Active Galactic Nuclei
The Astrophysical Journal, 2023 We present new estimates on the fraction of heavily X-ray-obscured, Compton-thick (CT) active galactic nuclei (AGNs) out to a redshift of z ≤ 0.8. From a sample of 540 AGNs selected by mid-infrared (MIR) properties in observed X-ray survey fields, we ...
Christopher M. Carroll +7 more
doaj +1 more source
X-RAY LUMINOSITY FUNCTIONS OF ACTIVE GALACTIC NUCLEI [PDF]
Multiwavelength AGN Surveys, 2004 To appear in the proceedings of the conference "Multiwavelenth AGN Surveys", held in Cozumel, Mexico, December 2003 (invited talk).
openaire +3 more sources
X-ray variability of active galactic nuclei and the flare model [PDF]
Advances in Space Research, 2006 Short-term variability of X-ray spectra has been reported for several Active Galactic Nuclei. Significant X-ray flux variations are observed within time scales down to 10^4 -- 10^5 seconds. We discuss short variability time scales in the framework of the X-ray flare model, which assumes the release of a large hard X-ray flux above a small portion of ...
M. Mouchet +7 more
openaire +5 more sources
A Simple Method for Predicting N H Variability in Active Galactic Nuclei
The Astrophysical Journal, 2023 The unified model of active galactic nuclei (AGNs) includes a geometrically thick obscuring medium to explain the differences between type I and type II AGNs as an effect of inclination angle.
Isaiah S. Cox +6 more
doaj +1 more source