Results 21 to 30 of about 1,482 (185)
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
openaire +4 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
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
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
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 +3 more sources
Variability and the X-ray/UV ratio of active galactic nuclei [PDF]
Astronomy and Astrophysics, 2010 16 pages, 10 figures, 1 table.
VAGNETTI, FAUSTO +3 more
openaire +6 more sources
X-rays from active galactic nuclei
The Astrophysical Journal, 1981 Through detailed numerical calculations, we have shown that production of thermal photons at the self-absorbed cyclotron higher harmonics and Comptonization of those soft photons in a hot plasma with the electron temperature 10/sup 9/ K provide a natural mechanism to account for the dominant observed features of the X-ray emission in the active ...
Sachiko Tsuruta +2 more
openaire +2 more sources
Review on Active-Galactic Nuclei at hard X-ray energies [PDF]
Proceedings of An INTEGRAL view of the high-energy sky (the first 10 years) - 9th INTEGRAL Workshop and celebration of the 10th anniversary of the launch — PoS(INTEGRAL 2012), 2013 Hard X-ray surveys are an important tool for the study of active galactic nuclei (AGN): they provide almost an unbiased view of absorption in the extragalactic population, allow the study of spectral features such as reflection and high energy cut-off which would otherwise be unexplored and favour the discovery of some blazars at high redshift.
R. Landi +8 more
openaire +2 more sources
Soft X-ray active galactic nuclei
The Astrophysical Journal, 1984 The discovery of 10 active galactic nuclei (AGNs) based upon optical observations of Einstein Observatory X-ray sources is reported. The new objects are optically similar to AGNs that have been identified by others with this technique. One notable exception, the quasar E1821 + 643, is associated with a previously unidentified X-ray source detected with
F. E. Marshall, S. H. Pravdo
openaire +2 more sources
X-ray variability time scales in active galactic nuclei [PDF]
Astronomy & Astrophysics, 2009 6 pages, 1 figure, accepted for publication in Astronomy and ...
W. Ishibashi, T. J. L. Courvoisier
openaire +3 more sources