Results 301 to 310 of about 117,210 (326)

One month convection timescale on the surface of a giant evolved star. [PDF]

Nature
Vlemmings W, Khouri T, Bojnordi Arbab B, De Beck E, Maercker M.   +4 more
europepmc   +1 more source

Effect of station selection on VLBI-to-GNSS orientation transfer using space-ties onboard a next generation Galileo satellite

Sert H, Hugentobler U, Karatekin Ö, Dehant V.   +3 more
europepmc   +1 more source

Flying through an Eruption-associated Magnetic Reconnection Current Sheet in the Solar Corona

Patel R, Niembro T, Xie X, Seaton D, Badman S, Roy S, Rivera Y, Reeves K, Stenborg G, Hess P, West M, Feller A, Hirzberger J, Suarez DO, Solanki S, Strecker H, Valori G.   +16 more
europepmc   +1 more source

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Unified models for active galactic nuclei and quasars

, 1993
Because the critical central regions of Active Galactic Nuclei (AGN) and quasars are strongly nonspherical but spatially unresolved, orientation effects have been the source of much confusion. In fact, it now appears that much of the variety in AGN types
R. Antonucci
semanticscholar   +1 more source

Quasars: The Observational Perspectives [PDF]

, 2012
The empirical basis of quasar astronomy can be overawing especially in the twenty-first century. A first source of intricacy involves the nomenclature that has evolved to label the multifold phenomenological manifestations now united under the umbrella of active galactic nuclei (AGNs). A further complication involves observations of the many subclasses
Jack W. Sulentic, Mauro D'Onofrio, S. Zamfir, Deborah Dultzin, Dirk Grupe, Alberto Franceschini, Sergey G. Sergeev, Luigi Foschini, Tracey Jane Turner, Martin Gaskell, V. I. Pronik, Paola Marziani, Aleksander Volvach, Raffaella Morganti, Raffaella Morganti, Todd A. Boroson, Heino Falcke, Heino Falcke, Ajit Kembhavi, Gordon T. Richards, Michael R. S. Hawkins, Yuri Neshpor, Greg Shields, Ari Laor, Martin Elvis, Elmar Körding   +25 more
openaire   +5 more sources

Cosmological constraints from the Hubble diagram of quasars at high redshifts

Nature Astronomy, 2018
The concordance model (Λ cold dark matter (ΛCDM) model, where Λ is the cosmological constant) reproduces the main current cosmological observations1–4 assuming the validity of general relativity at all scales and epochs and the presence of CDM and of Λ ...
G. Risaliti, E. Lusso
semanticscholar   +1 more source

Quasars

Applied Optics, 1966
A short historical outline of the discovery and a description of observed properties of quasars introduces questions as to their nature. Some of the principal arguments concerning their reality, distance, intrinsic properties and age lead to the conclusion that, while there is room for other points of view; a strong case can be made for the ...
openaire   +2 more sources

Bayesian Quasar Selection and the Quasar Luminosity Function

AIP Conference Proceedings, 2008
I summarize our work on the construction of deep photometric quasar catalogs using a non‐parametric Bayesian classifier based on kernel density estimation. Using only 5‐band optical data from the Sloan Digital Sky Survey (SDSS), we have identified nearly 1,000,000 photometric quasars candidates over ...
Gordon T. Richards, Coryn A.L. Bailer-Jones   +1 more
openaire   +2 more sources

Oscillations of Quasars

Science, 1964
Rotation in addition to free gravitational motion can produce oscillations in a large spherical mass of gas. The theory may provide an explanation of the variations of brightness in such objects as 3C273.
openaire   +3 more sources

Quasars and Superclusters

Symposium - International Astronomical Union, 1983
The topic of quasars and superclusters is only a few years old. Although the first pairs of quasars with small angular separations on the sky were found ten years ago (Stockton 1972, Wampler et al. 1973), the pair members had very different redshifts.
openaire   +2 more sources