Results 31 to 40 of about 9,238,867 (222)
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 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.
Contini, M. +2 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
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 ...
F. Takahara, S. Tsuruta, S. Ichimaru
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X-ray variability time scales in active galactic nuclei [PDF]
Astronomy & Astrophysics, 2009 6 pages, 1 figure, accepted for publication in Astronomy and ...
Ishibashi, W., Courvoisier, T. J. -L.
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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
S. H. Pravdo, F. E. Marshall
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The ratio of X-ray-to-optical luminosity for active galactic nuclei [PDF]
Monthly Notices of the Royal Astronomical Society, 1984 On montre que le renforcement apparent du rapport moyen des luminosites RX a optique des noyaux de Seyfert 1, en comparaison avec les QSO radio calmes, peut etre largement, sinon totalement, du a un rougissement interne.
CHENG FZ +3 more
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Active Galactic Nuclei and their demography through cosmic time [PDF]
, 2022 Active Galactic Nuclei (AGN) are highly energetic astrophysical sources powered by accretion onto supermassive black holes in galaxies, which present unique observational signatures covering the full electromagnetic spectrum (and more) over about twenty ...
Mainieri, Vincenzo +2 more
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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 ...
Goosmann, R. W. +6 more
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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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