Results 21 to 30 of about 1,919 (235)
X-Ray Variability of Active Galactic Nuclei [PDF]
Highlights of Astronomy, 1983 X-ray variability of active galactic nuclei is commonplace on scales from days to years. It also occurs, although rarely, on time scales as short as 200 seconds. Both these statements must be strongly qualified by the irregularity and insensitivity of the available observations. In the X-rays we expect that we are seeing deep within the active nucleus,
Greg Madejski +2 more
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The Astrophysical Journal, 2023 To understand the formation and growth of supermassive black holes (SMBHs) and their coevolution with host galaxies, it is essential to know the impact of environment on the activity of active galactic nuclei (AGNs).
Zhensong Hu +16 more
doaj +1 more source
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
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The Astrophysical Journal, 2023 1ES1927+654 is a nearby active galactic nucleus (AGN) that has shown an enigmatic outburst in optical/UV followed by X-rays, exhibiting strange variability patterns at timescales of months to years.
Ritesh Ghosh +26 more
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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 ...
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The X-Ray Properties of 2MASS Red Active Galactic Nuclei [PDF]
The Astrophysical Journal, 2002 The Two Micron All Sky Survey (2MASS) is finding previously unidentified, luminous red active galactic nuclei (AGN). This new sample has a space density similar to, or greater than, previously known AGN, suggesting that a large fraction of the overall population has been missed. Chandra observations of a well-defined subset of these objects reveal that
Wilkes, Belinda +6 more
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BASS. XXII. The BASS DR2 AGN Catalog and Data
The Astrophysical Journal Supplement Series, 2022 We present the active galactic nucleus (AGN) catalog and optical spectroscopy for the second data release of the Swift BAT AGN Spectroscopic Survey (BASS DR2).
Michael J. Koss +34 more
doaj +1 more source
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.
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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).
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Active Galactic Nuclei Unification and the X‐Ray Background [PDF]
The Astrophysical Journal, 2005 Active galactic nuclei (AGNs) unification, which implies a large number of obscured AGNs, can explain the optical, infrared, and X-ray content of deep multiwavelength surveys. Here we show that the same model also successfully explains the spectral shape and intensity of the X-ray background. The simplest possible unified model assumes a constant ratio
Ezequiel Treister +2 more
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