Results 51 to 60 of about 275,801 (258)

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

AGN STORM 2. III. A NICER View of the Variable X-Ray Obscurer in Mrk 817

The Astrophysical Journal, 2023
The AGN STORM 2 Collaboration targeted the Seyfert 1 galaxy Mrk 817 for a year-long multiwavelength, coordinated reverberation mapping campaign including Hubble Space Telescope, Swift, XMM-Newton, NICER, and ground-based observatories. Early observations
Ethan R. Partington, Edward M. Cackett, Erin Kara, Gerard A. Kriss, Aaron J. Barth, Gisella De Rosa, Y. Homayouni, Keith Horne, Hermine Landt, Abderahmen Zoghbi, Rick Edelson, Nahum Arav, Benjamin D. Boizelle, Misty C. Bentz, Michael S. Brotherton, Doyee Byun, Elena Dalla Bontà, Maryam Dehghanian, Pu Du, Carina Fian, Alexei V. Filippenko, Jonathan Gelbord, Michael R. Goad, Diego H. González Buitrago, Catherine J. Grier, Patrick B. Hall, Chen Hu, Dragana Ilić, Michael D. Joner, Shai Kaspi, Christopher S. Kochanek, Kirk T. Korista, Andjelka B. Kovačević, Daniel Kynoch, Jacob N. McLane, Missagh Mehdipour, Jake A. Miller, Christos Panagiotou, Rachel Plesha, Luka Č. Popović, Daniel Proga, Daniele Rogantini, Thaisa Storchi-Bergmann, David Sanmartim, Matthew R. Siebert, Marianne Vestergaard, Martin J. Ward, Tim Waters, Fatima Zaidouni   +48 more
doaj   +1 more source

'Disc-jet' coupling in black hole X-ray binaries and active galactic nuclei [PDF]

Lect.Notes Phys.794:115-142,2010, 2009
In this chapter I will review the status of our phenomenological understanding of the relation between accretion and outflows in accreting black hole systems. This understanding arises primarily from observing the relation between X-ray and longer wavelength (infrared, radio) emission.
arxiv   +1 more source

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 orders of magnitude in frequency.
arxiv   +1 more source

X-RAY VARIABILITY AND THE INNER REGION IN ACTIVE GALACTIC NUCLEI [PDF]

The Astrophysical Journal, 2014
32 pages, 11 figures (9 sub-figures); 4 Tables; 1 appendix; published in the Astrophysical ...
P. Mohan, A. Mangalam
openaire   +4 more sources

Cosmic X-ray surveys of Active Galactic Nuclei: synergy between X-ray and infrared observations [PDF]

, 2016
We briefly review the synergy between X-ray and infrared observations for Active Galactic Nuclei (AGNs) detected in cosmic X-ray surveys, primarily with XMM-Newton, Chandra, and NuSTAR. We focus on two complementary aspects of this X-ray-infrared synergy (1) the identification of the most heavily obscured AGNs and (2) the connection between star ...
arxiv   +1 more source

X-ray Reverberation Observational Modelling in Active Galactic Nuclei [PDF]

Proceedings of Accretion Processes in Cosmic Sources – II — PoS(APCS2018), 2019
X-ray reverberation in Active Galactic Nuclei, believed to be the result of the reprocessing of coronal photons by the underlying accretion disc, has allowed us to probe the properties of the inner-most regions of the accretion flow and the central black hole. Our current model (KYNREFREV) computes the time-dependent reflection spectra of the disc as a
V. Karasa, I. Papadakiscd, M. Dovčiaka, Maria Dolores Caballero Garcia, M. Bursaa   +4 more
openaire   +3 more sources

X-ray variability of 104 active galactic nuclei [PDF]

Proceedings of the International Astronomical Union, 2012
AbstractWe have performed a uniform analysis of the power spectrum densities (PSDs) of 104 nearby (z<0.4) active galactic nuclei (AGN) using 209 XMM-Newton/pn observations, including several AGN classes. These PSDs span ≃ 3 decades in temporal frequencies, ranging from minutes to days.
O. González-Martín, Simon Vaughan
openaire   +2 more sources

On the Cosmic Evolution of AGN Obscuration and the X-Ray Luminosity Function: XMM-Newton and Chandra Spectral Analysis of the 31.3 deg2 Stripe 82X

The Astrophysical Journal, 2023
We present X-ray spectral analysis of XMM-Newton and Chandra observations in the 31.3 deg ^2 Stripe-82X (S82X) field. Of the 6181 unique X-ray sources in this field, we analyze a sample of 2937 candidate active galactic nuclei (AGNs) with solid redshifts
Alessandro Peca, Nico Cappelluti, C. Megan Urry, Stephanie LaMassa, Stefano Marchesi, Tonima Tasnim Ananna, Mislav Baloković, David Sanders, Connor Auge, Ezequiel Treister, Meredith Powell, Tracey Jane Turner, Allison Kirkpatrick, Chuan Tian   +13 more
doaj   +1 more source

Discovery of very high energy gamma-rays associated with an X-ray binary [PDF]

Science 309:746-749,2005, 2005
X-ray binaries are composed of a normal star in orbit around a neutron star or stellar-mass black hole. Radio and X-ray observations have led to the presumption that some X-ray binaries called microquasars behave as scaled down active galactic nuclei. Microquasars have resolved radio emission that is thought to arise from a relativistic outflow akin to
arxiv   +1 more source