Results 161 to 170 of about 63,914 (268)
"Fermi" bubbles are bursting from our galaxy. Their origins remain a mystery. [PDF]
Proc Natl Acad Sci U S A, 2023 Mann A.
europepmc +1 more source
On the Extremely X-Ray Variable Active Galactic Nuclei in the XMM-LSS Field
The Astrophysical JournalWe present a systematic investigation of extremely X-ray variable active galactic nuclei (AGNs) in the ≈5.3 deg ^2 XMM-SERVS XMM-LSS region. Eight variable AGNs are identified with rest-frame 2 keV flux density variability amplitudes around 6–12.
Zijian Zhang +5 more
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Redshifted Iron Emission and Absorption Lines in the Chandra X-Ray Spectrum of Centaurus A
The Astrophysical JournalCen A hosts the closest active galactic nucleus to the Milky Way, which makes it an ideal target for investigating the dynamical processes in the vicinity of accreting supermassive black holes.
David Bogensberger +11 more
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The Astrophysical JournalThe X-ray quasiperiodic oscillation (QPO) is a remarkable form of variability in systems of compact object accretion. RE J1034+396, harboring the most significant X-ray QPO in active galactic nuclei (AGNs), is the most noteworthy source for in-depth ...
Ruisong Xia, Hao Liu, Yongquan Xue
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The Astrophysical Journal LettersQuasiperiodic oscillations (QPOs) have been widely observed in black hole X-ray binaries (BHBs), which often exhibit significant X-ray variations. Extensive research has explored the long-term evolution of the properties of QPOs in BHBs.
Ruisong Xia, Hao Liu, Yongquan Xue
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X-ray absorption in Active Galactic Nuclei
, 2015 I Nuclei Galattici Attivi (AGN) sono tra le sorgenti più luminose dell’Universo e sono osservati in circa 10-20% delle galassie nell’Universo locale. Il meccanismo di generazione dell’energia di queste sorgenti è l’accrescimento di materia su un buco nero supermassivo (SMBH). Secondo il paradigma del Modello Unificato (UM) il SMBH è circondato da un
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Obscured and unobscured X-ray active galactic nuclei
Astronomy & AstrophysicsContext. Active galactic nuclei (AGNs) play a crucial role in galaxy evolution by influencing the observational properties of their host galaxies. Aims. We aim to investigate the host-galaxy properties of X-ray selected AGNs, focusing on differences between obscured and unobscured AGNs, and between high-excitation sources (log([O III]λ5007/Hβ ≥ 0.5 ...
C. G. Bornancini, G. A. Oio, G. Coldwell
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X-ray emission mechanisms in active galactic nuclei
, 2016 Active Galactic Nuclei (AGN) are compact regions at the centre of active galaxies which are visible across the full electromagnetic spectrum. Their radiation comes from the accretion of matter onto a supermassive black hole. They are particularly bright in X-rays, showing several components in their spectra.
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The Astrophysical Journal LettersDynamic processes in the accretion flow near black holes produce X-ray flux variability, sometimes quasiperiodic. Determining its physical origin is key to mapping the accretion geometry but remains unresolved.
Qing-Cang Shui +9 more
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Active galaxies and the diffuse Gamma-Ray background [PDF]
A model for the origin of relativistic particles and gamma rays in active galactic nuclei and quasars, together with recent HEAO-1 observations of the spectra of active galaxies from 2 to 165 keV, provide the basis for a reexamination of the nature of ...
Kazanas, D., Protheroe, R. J.
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