Results 91 to 100 of about 9,238,867 (222)

Extreme X-Ray Iron Lines in Active Galactic Nuclei

The Astrophysical Journal, 2002
We analyze X-ray spectra of heavily obscured (N_H > 10^{24} cm^{-2}) active galaxies obtained with Chandra, concentrating on the iron K alpha fluorescence line. We measure very large equivalent widths in most cases, up to 5 keV in the most extreme example.
Levenson, N. A., Krolik, J. H., Zycki, P. T., Heckman, T. M., Weaver, K. A., Awaki, H., Terashima, Y.   +6 more
openaire   +2 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
Treister, Ezequiel, Urry, Claudia Megan
openaire   +2 more sources

Elusive active galactic nuclei [PDF]

, 2003
A fraction of active galactic nuclei do not show the classical Seyfert-type signatures in their optical spectra, i.e. they are optically 'elusive'. X-ray observations are an optimal tool to identify this class of objects.
BIANCHI, STEFANO, Comastri, A., GILLI R, Gilli, R., SALVATI M., KRABBE A, Boker, T., Matt, G., NAGAR N. M, MARCONI A, Marconi, A., COMASTRI A, MAIOLINO R, COLBERT E, BÖKER T, MATT G, Colbert, E., Krabbe, A., Maiolino, R., Salvati, M., Nagar, N. M., Bianchi, S.   +21 more
core   +2 more sources

Quasiperiodic Oscillation of RE J1034+396 Diagnosed with Phase-resolved Spectral Analysis

The Astrophysical Journal Letters
We analyze 10 XMM-Newton observations of the narrowline Seyfert 1 galaxy RE J1034+396 to investigate the origin of its quasiperiodic oscillation (QPO).
Wen-Zhong Li, Shu Zhang, Qing-Cang Shui, Yu-Peng Chen, Shuang-Nan Zhang, Hua Feng, Ming-Yu Ge, Lian Tao, Jing-Qiang Peng, Bo-Yan Chen, Ling- Da Kong, Peng-Ju Wang   +11 more
doaj   +1 more source

Physics from Time Variability of the VHE Blazar PKS 2155-304 [PDF]

, 2010
Blazars are the principal extragalactic sources of very high energy gamma-ray emission in the Universe. These objects constitute a sub-class of Active Galactic Nuclei whose emission is dominated by Doppler boosted non-thermal radiation from plasma ...
BARRES-DE-ALMEIDA, ULISSES
core  

The Gamma Factory: A New Experimental Paradigm for the Post‐HL‐LHC Era

Annalen der Physik, Volume 538, Issue 8, August 2026.
ABSTRACT The Gamma Factory (GF) proposal is motivated by the recognition of a largely untapped potential of the CERN accelerator complex to enable a new research program at the intersection of particle, nuclear, atomic, fundamental, and applied physics. These fields could benefit from novel experimental tools made possible by a future GF facility.
Mieczyslaw Witold Krasny
wiley   +1 more source

The Role of Environment in Triggering Active Galactic Nuclei—Evidence for a Change at z ∼ 1

The Astrophysical Journal
What triggers active galactic nuclei (AGN) in some galaxies and what role this brief period of activity plays in the overall evolution of galaxies are still open questions. This paper explores whether or not the local, on scales of ≈1 Mpc, galaxy density
Jason R. Reeves, Anna Sajina, Henry Adair, Duncan Farrah, Mark Lacy   +4 more
doaj   +1 more source

Early–Late Carboniferous Tectonic Evolution of the Northern North China Craton (NE China): Constraints From Zircon Ages, Geochemistry, and Crustal Thickness Modeling

Geochemistry, Geophysics, Geosystems, Volume 27, Issue 8, August 2026.
Abstract The tectonic evolution of the northern margin of the North China Craton (NCC) remains controversial. In this study, we obtained zircon U–Pb ages, geochemical data, and Sr–Nd isotopic data for volcanic rocks, and detrital zircon ages for sedimentary rocks from the Yufutun, Tongqigou, and Benxi formations in central‐southern Jilin Province, NE ...
Yunfei Chang, Qingxiang Du, Huachun Gan, Xiaoli Shen, Zuozhen Han, Xiaoxue Hou, Huicong Zhang   +6 more
wiley   +1 more source

A Systematic Search for X-Ray Eclipse Events in Active Galactic Nuclei Observed by Swift

The Astrophysical Journal
The nuclear regions of active galactic nuclei (AGNs) likely host clumpy clouds that occasionally obscure the central X-ray source, causing eclipse events. These events offer a unique opportunity to study the properties and origins of such clouds. However,
Tianying Lian, Chichuan Jin, Weimin Yuan
doaj   +1 more source

Radio sources in the Chandra Galactic Bulge Survey [PDF]

, 2012
We discuss radio sources in the Chandra Galactic Bulge Survey region. By cross-matching the X-ray sources in this field with the NRAO VLA Sky Survey archival data, we find 12 candidate matches.
Maccarone, M.C., MacCarone, Thomas J., Steeghs, Danny, Maccarone, T. J., Wijnands, R., Steeghs, D., Britt, Christopher T., Hynes, R.I., Torres, Manuel A.P., Wijnands, Rudy, Torres, M. A. P., Britt, C.T., Jonker, Peter G., Hynes, R. I., Nelemans, Gijs, Jonker, P. G., Hynes, Robert I., Torres, M.A.P., Jonker, P.G., Greiss, Sandra, Nelemans, G., Maccarone, T.J., Nelemans, G.A., Greiss, S., Britt, Christopher B. T.   +24 more
core   +3 more sources