Results 11 to 20 of about 30,807 (267)

Deep Extragalactic X-Ray Surveys

Annual Review of Astronomy and Astrophysics, 2005
▪ Abstract  Deep surveys of the cosmic X-ray background are reviewed in the context of observational progress enabled by the Chandra X-Ray Observatory and the X-Ray Multi-Mirror Mission-Newton. The sources found by deep surveys are described along with their redshift and luminosity distributions, and the effectiveness of such surveys at selecting ...
Brandt, W., Hasinger, G.
openaire   +3 more sources

A High Fraction of Heavily X-Ray-obscured Active Galactic Nuclei

The Astrophysical Journal, 2023
We present new estimates on the fraction of heavily X-ray-obscured, Compton-thick (CT) active galactic nuclei (AGNs) out to a redshift of z ≤ 0.8. From a sample of 540 AGNs selected by mid-infrared (MIR) properties in observed X-ray survey fields, we ...
Christopher M. Carroll, Tonima T. Ananna, Ryan C. Hickox, Alberto Masini, Roberto J. Assef, Daniel Stern, Chien-Ting J. Chen, Lauranne Lanz   +7 more
doaj   +1 more source

Constraints From Dwarf Galaxies on Black Hole Seeding and Growth Models With Current and Future Surveys

The Astrophysical Journal, 2023
Dwarf galaxies are promising test beds for constraining models of supermassive and intermediate-mass black holes (MBHs) via their BH occupation fraction (BHOF).
Urmila Chadayammuri, Ákos Bogdán, Angelo Ricarte, Priyamvada Natarajan   +3 more
doaj   +1 more source

Survey of X-ray pulsars in hard X-rays [PDF]

Proceedings of The Extreme sky: Sampling the Universe above 10 keV — PoS(extremesky2009), 2010
Results of spectral, timing and spatial analysis of X-ray pulsars in hard X-rays are briefly discussed. Using data of INTEGRAL, XMM-Newton and Chandra observatories we determined an optical counterparts and distances for several X-ray pulsars and built the spatial distribution of this class objects in the Galaxy. Variations of the cyclotron line energy
Alexander Lutovinov, Sergey Tsygankov
openaire   +1 more source

BASS. XXI. The Data Release 2 Overview

The Astrophysical Journal Supplement Series, 2022
The BAT AGN Spectroscopic Survey (BASS) is designed to provide a highly complete census of the key physical parameters of the supermassive black holes (SMBHs) that power local active galactic nuclei (AGNs) ( z ≲ 0.3), including their bolometric ...
Michael J. Koss, Benny Trakhtenbrot, Claudio Ricci, Franz E. Bauer, Ezequiel Treister, Richard Mushotzky, C. Megan Urry, Tonima T. Ananna, Mislav Baloković, Jakob S. den Brok, S. Bradley Cenko, Fiona Harrison, Kohei Ichikawa, Isabella Lamperti, Amy Lein, Julian E. Mejía-Restrepo, Kyuseok Oh, Fabio Pacucci, Ryan W. Pfeifle, Meredith C. Powell, George C. Privon, Federica Ricci, Mara Salvato, Kevin Schawinski, Taro Shimizu, Krista L. Smith, Daniel Stern   +26 more
doaj   +1 more source

An Optically Discovered Outburst from XTE J1859+226

The Astrophysical Journal, 2023
Using the Zwicky Transient Facility, in 2021 February we identified the first known outburst of the black hole X-ray transient XTE J1859+226 since its discovery in 1999. The outburst was visible at X-ray, UV, and optical wavelengths for less than 20 days,
Eric C. Bellm, Yuankun Wang, Jan van Roestel, Rebecca A. Phillipson, Michael W. Coughlin, John A. Tomsick, Steven L. Groom, Brian Healy, Josiah Purdum, Ben Rusholme, Jesper Sollerman, Peter Bealo, Stefano Lora, Eddy Muyllaert, Ivo Peretto, Erik J. Schwendeman   +15 more
doaj   +1 more source

X-ray spectroscopic survey of highly accreting AGN [PDF]

Astronomy & Astrophysics, 2022
Improving our understanding of the nuclear properties of high-Eddington-ratio (λEdd) active galactic nuclei (AGN) is necessary since at this regime the radiation pressure is expected to affect the structure and efficiency of the accretion disc-corona system.
M. Laurenti, E. Piconcelli, L. Zappacosta, F. Tombesi, C. Vignali, S. Bianchi, P. Marziani, F. Vagnetti, A. Bongiorno, M. Bischetti, A. del Olmo, G. Lanzuisi, A. Luminari, R. Middei, M. Perri, C. Ricci, G. Vietri   +16 more
openaire   +6 more sources

X-Ray Surveys

, 1998
A review of recent developments in the field of X-ray surveys, especially in the hard (2-10 and 5-10 keV) bands, is given. A new detailed comparison between the measurements in the hard band and extrapolations from ROSAT counts, that takes into proper account the observed distribution of spectral slopes, is presented.
Giommi, P., Fiore, F., Perri, M.
openaire   +2 more sources

TheSwiftX-ray Telescope Cluster Survey [PDF]

Astronomy & Astrophysics, 2014
(Abridged) We present a spectral analysis of a new, flux-limited sample of 72 X-ray selected clusters of galaxies identified with the X-ray Telescope (XRT) on board the Swift satellite down to a flux limit of ~10-14 erg/s/cm2 (SWXCS, Tundo et al. 2012).
Tozzi, P., Moretti, A., Tundo, E., Liu, T., Rosati, P., BORGANI, STEFANO, Tagliaferri, G., Campana, S., Fugazza, D., D'Avanzo, P.   +9 more
openaire   +3 more sources

The Soft X-ray Excess in Quasars and Deep X-ray Surveys [PDF]

Symposium - International Astronomical Union, 1994
We examine the surface density of quasars expected in the ROSAT PSPC surveys, using quasar optical luminosity functions and model continuum spectra including a soft X-ray excess. We show that the surface density is a sensitive function of the characteristic energy of the soft excess, and the absorption within the quasar as well as the interstellar ...
Ajit Kembhavi, A. C. Fabian
openaire   +1 more source