Results 31 to 40 of about 50,755 (263)
X-ray variability of 104 active galactic nuclei [PDF]
Proceedings of the International Astronomical Union, 2012 AbstractWe have performed a uniform analysis of the power spectrum densities (PSDs) of 104 nearby (z<0.4) active galactic nuclei (AGN) using 209 XMM-Newton/pn observations, including several AGN classes. These PSDs span ≃ 3 decades in temporal frequencies, ranging from minutes to days.
O. González-Martín, S. Vaughan
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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
, 2002 A significant correlation between FeKalpha line energy and X-ray spectral slope has been discovered among radio-quiet active galactic nuclei. The ionization stage of the bulk of the FeKalpha emitting material is not the same in all active galactic nuclei
Arnaud K. A. +14 more
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A Hard Look at NGC 5347: Revealing a Nearby Compton-thick AGN [PDF]
, 2019 Current measurements show that the observed fraction of Compton-thick (CT) active galactic nuclei (AGN) is smaller than the expected values needed to explain the cosmic X-ray background. Prior fits to the X-ray spectrum of the nearby Seyfert-2 galaxy NGC
Barret, D. +13 more
core +6 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
Hard X-ray variability of active galactic nuclei [PDF]
Astronomy & Astrophysics, 2007 Aims. Active Galactic Nuclei are known to be variable throughout the electromagnetic spectrum. An energy domain poorly studied in this respect is the hard X-ray range above 20 keV. Methods. The first 9 months of the Swift/BAT all-sky survey are used to study the 14-195 keV variability of the 44 brightest AGN. The sources have been selected due to their
V. Beckmann +6 more
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Cosmic X-ray Background from Early Active Galactic Nuclei [PDF]
International Astronomical Union Colloquium, 1989 A model for the origin of the cosmic X-ray background (hereafter XRB) is presented. The component of the background left after subtraction of the known classes of sources is explained by emission from a population of black hole sources at the redshift of z ~ 4-5. The model is presented in more detail elsewhere (Zdziarski 1988).
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The anti-correlation between the hard X-ray photon index and the Eddington ratio in LLAGNs
, 2009 We find a significant anti-correlation between the hard X-ray photon index and the Eddington ratio L_Bol/L_Edd for a sample of Low-Ionization Nuclear Emission-line Regions (LINERs) and local Seyfert galaxies, compiled from literatures with Chandra or XMM-
Bian +65 more
core +2 more sources
A UV to X-Ray View of Soft Excess in Type 1 Active Galactic Nuclei. II. Broadband Correlations
The Astrophysical JournalThe physical origin of soft X-ray excess (SE) is a long-lasting question, with two prevailing theories—“warm corona” and “ionized reflection”—dominating the discussion.
Shi-Jiang Chen +7 more
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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
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