Results 31 to 40 of about 1,919 (235)
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-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
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
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-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
Ultraviolet and X-ray variability of active galactic nuclei withSwift [PDF]
Monthly Notices of the Royal Astronomical Society, 2016 14 pages, 8 figures, 4 tables in main text, plus 15 pages of figures in appendices.
D. J. K. Buisson +3 more
openaire +3 more sources
The infrared--X-ray continuum correlation in active galactic nuclei [PDF]
Monthly Notices of the Royal Astronomical Society, 2003 The correlation between the soft X-ray and near infrared emission from AGN is analysed using composite models by the code SUMA. We find new evidences for differences in ranges of parameters which characterize the NLR of Seyfert galaxies and LINERs. Results obtained by modelling the Einstein and the ROSAT samples of galaxies are in full agreement.
P. E. Campos +2 more
openaire +3 more sources