Results 171 to 180 of about 289,816 (297)

X-ray variability observed with HEAO A-1 [PDF]

Results from the HEAO A-1 instrument which observed X-ray source variability over a wide range of accessible timescales are surveyed. The objects observed include quasars, BL Lacertae, and active galactic nuclei.
Friedman, H.
core   +1 more source

X-ray astronomical spectroscopy [PDF]

The current status of the X-ray spectroscopy of celestial X-ray sources, ranging from nearby stars to distant quasars, is reviewed. Particular emphasis is placed on the role of such spectroscopy as a useful and unique tool in the elucidation of the ...
Holt, S. S.
core   +1 more source

X-raying Active Galaxies Found and Missed by the Sloan Digital Sky Survey [PDF]

arXiv, 2003
Current X-ray observatories, archival X-ray data, and the Sloan Digital Sky Survey (SDSS) represent a powerful combination for addressing key questions about active galactic nuclei (AGN). We describe a few selected issues at the forefront of X-ray AGN research and the relevance of the SDSS to them.
arxiv  

Accretion, ejection and reprocessing in supermassive black holes

, 2015
This is a White Paper in support of the mission concept of the Large Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We discuss the potential of LOFT for the study of active galactic nuclei.
Bianchi, S., Cappi, M., Czerny, B., Dadina, M., De Marco, B., De Rosa, A., Dovciak, M., Giroletti, M., Karas, V., Kunneriath, D., La Franca, F., Manousakis, A., Marinucci, A., Markowitz, A., McHardy, I., Mehdipour, M., Miniutti, G., Paltani, S., Paolillo, M., Papadakis, I., Perez-Torres, M., Peterson, B., Petrucci, P. O., Piconcelli, E., Ponti, G., Risaliti, G., Rozanska, A., Salvati, M., Sobolewska, M., Svoboda, J., Tombesi, F., Trevese, D., Uttley, P., Vagnetti, F., Vaughan, S., Vignali, C., Vincent, F. H., Zdziarski, A.   +37 more
core  

Connecting the X-Ray/UV Variability of Fairall 9 with NICER: A Possible Warm Corona

The Astrophysical Journal
The Seyfert 1 active galactic nucleus Fairall 9 was targeted by NICER, Swift, and ground-based observatories for a ∼1000 day long reverberation mapping campaign.
Ethan R. Partington, Edward M. Cackett, Rick Edelson, Keith Horne, Jonathan Gelbord, Erin Kara, Christian Malacaria, Jake A. Miller, James F. Steiner, Andrea Sanna   +9 more
doaj   +1 more source

Cosmic X-ray Background from Early Active Galactic Nuclei [PDF]

, 1989
A. A. Zdziarski
openalex   +1 more source

Demography of obscured and unobscured AGN: prospects for a Wide Field X-ray Telescope

, 2010
We discuss some of the main open issues in the evolution of Active Galactic Nuclei which can be solved by the sensitive, wide area surveys to be performed by the proposed Wide Field X-ray Telescope mission.Comment: Proceedings of "The Wide Field X-ray ...
A. Comastri, C. Vignali, E. Lusso, F. Marulli, M. Brusa, P. Rosati, P. Tozzi, PAOLILLO, MAURIZIO, R. Gilli, S. Borgani, the WFXT team   +10 more
core  

INTEGRAL/IBIS 7-year All-Sky Hard X-Ray Survey. Part II: Catalog of Sources

, 2010
This paper is the second in a series devoted to the hard X-ray (17-60 keV) whole sky survey performed by the INTEGRAL observatory over seven years. Here we present a catalog of detected sources which includes 521 objects, 449 of which exceed a 5 sigma ...
Abdo, Ajello, Aleksandrovich, Altamirano, Augello, Barlow, Barlow, Barthelmy, Bassa, Bassani, Bassani, Bassani, Bassani, Bazzano, Beckmann, Beckmann, Bikmaev, Bikmaev, Bikmaev, Bikmaev, Bird, Bird, Bird, Bird, Bodaghee, Brandt, Brandt, Brandt, Brandt, Brunschweiger, Burenin, Burenin, Burenin, Burenin, Burenin, Butler, Butters, Bykov, Bykov, Bélanger, Cackett, Cadol le Bel, Chaty, Chelovekov, Chelovekov, Chelovekov, Chelovekov, Chernyakova, Chernyakova, Chernyakova, Cornelisse, Courvoisier, Crawford, Cusumano, Dean, Den Hartog, den Hartog, den Hartog, Donato, E. Churazov, Enya, Fiocchi, Fisher, Galloway, Gehrels, Gotz, Grebenev, Grebenev, Grebenev, Grebenev, Grebenev, Grebenev, Grebenev, Grebenev, Grebenev, Grebenev, Grebenev, Grebenev, Grebenev, Grebenev, Grebenev, Gros, Gänsicke, Halpern, Hannikainen, Im, in ’t Zand, in ’t Zand, Jauncey, Karasev, Karasev, Keek, Kniazev, Kniazev, Kretschmar, Krivonos, Krivonos, Krivonos, Krivonos, Krivonos, Krivonos, Kuiper, Kuiper, Kuiper, Kuiper, Kuulkers, Kuulkers, Landi, Landi, Landi, Landi, Leyder, Liu, Liu, Lubinski, Lutovinov, Lutovinov, Lutovinov, Lutovinov, Lutovinov, Lutovinov, Lutovinov, Lutovinov, Lutovinov, Lutovinov, Lutovinov, M. Revnivtsev, Malizia, Malizia, Markwardt, Markwardt, Masetti, Masetti, Masetti, Masetti, Masetti, Masetti, Masetti, Masetti, Masetti, Masetti, Masetti, Masetti, Masetti, Masetti, Masetti, Mescheryakov, Molkov, Molkov, Molkov, Morelli, Negueruela, Negueruela, Nespoli, Paizis, Palmer, Parisi, Patel, Pavlinskii, Potter, Produit, R. Krivonos, R. Sunyaev, Ratti, Rea, Reig, Reig, Renaud, Revnivtsev, Revnivtsev, Revnivtsev, Revnivtsev, Revnivtsev, Revnivtsev, Revnivtsev, Revnivtsev, Revnivtsev, Revnivtsev, Rodriguez, Rodriguez, Rodriguez, Rodriguez, Rodriguez, S. Grebenev, S. Tsygankov, Sazonov, Sazonov, Sazonov, Sguera, Sguera, Sidoli, Smith, Soldi, Soldi, Steeghs, Sunyaev, Sunyaev, Sunyaev, Terrier, Tomsick, Tomsick, Tomsick, Tomsick, Tomsick, Tomsick, Torrejón, Torres, Torres, Tueller, Tueller, Turler, Ubertini, Ubertini, Walter, Walter, Watson, Wijnands, Winkler, Winter, Zhou, Zurita Heras   +220 more
core   +1 more source

Hydrogen Column Density Variability in a Sample of Local Compton-thin AGN II

The Astrophysical Journal
We present the multiepoch analysis of 13 variable, nearby ( z ≲ 0.1), and Compton-thin (10 ^22 < N _H < 1.5 × 10 ^24 cm ^−2 ) active galactic nuclei (AGN) selected from the 105-month BAT catalog.
A. Pizzetti, N. Torres-Albà, S. Marchesi, J. Buchner, I. Cox, X. Zhao, S. Neal, D. Sengupta, R. Silver, M. Ajello   +9 more
doaj   +1 more source

X-Ray and Near-Infrared Spectroscopy of Dim X-Ray Point Sources Constituting the Galactic Ridge X-Ray Emission

Acta Polytechnica CTU Proceedings, 2014
We present the results of X-ray and Near-Infrared observations of the Galactic Ridge X-ray Emission (GRXE). We extracted 2,002 X-ray point sources in the Chandra Bulge Field (l =0°.113, b = 1°.424) down to ~10-14.8 ergscm-2s-1 in 2-8 keV band with the ...
Kumiko Morihana, Masahiro Tsujimoto, Ken Ebisawa   +2 more
doaj   +1 more source