Results 41 to 50 of about 110,927 (295)
Do Quasars Lens Quasars? [PDF]
The Astrophysical Journal, 1997 If the unexpectedly high frequency of quasar pairs with very different component redshifts is due to the lensing of a population of background quasars by the foreground quasar, typical lens masses must be $\sim10^{12}M_{\sun}$ and the sum of all such quasar lenses would have to contain $\sim0.005$ times the closure density of the Universe.
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Finding Multiply Lensed and Binary Quasars in the DESI Legacy Imaging Surveys
The Astrophysical Journal Supplement Series, 2023 The time delay between multiple images of strongly lensed quasars is a powerful tool for measuring the Hubble constant ( H _0 ). To achieve H _0 measurements with higher precision and accuracy using the time delay, it is crucial to expand the sample of ...
C. Dawes +6 more
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Redshift-weighted constraints on primordial non-Gaussianity from the clustering of the eBOSS DR14 quasars in Fourier space [PDF]
Journal of Cosmology and Astroparticle Physics, 2019 We present constraints on local primordial non-Gaussianity (PNG), parametrized through fNLloc, using the Sloan Digital Sky Survey IV extended Baryon Oscillation Spectroscopic Survey Data Release 14 quasar sample.
E. Castorina +15 more
semanticscholar +1 more source
Proceedings of the International Astronomical Union, 2014 AbstractAlthough the extragalactic nature of 3C 48 and other quasi stellar radio sources was discussed as early as 1960 by John Bolton and others, it was rejected largely because of preconceived ideas about what appeared to be unrealistically high radio and optical luminosities.
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Constraining the anisotropy of the Universe with the X-ray and UV fluxes of quasars
European Physical Journal C: Particles and Fields, 2021 We test the anisotropy in the Finslerian cosmological model with the X-ray and ultraviolet (UV) fluxes of quasars. The 2015 and 2020 compilations of quasars are used in the cosmological constraints.
Dong Zhao, Jun-Qing Xia
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Changing-look Quasar Candidates: First Results from Follow-up Spectroscopy of Highly Optically Variable Quasars [PDF]
Astrophysical Journal, 2018 Active galactic nuclei (AGNs) that show strong rest-frame optical/UV variability in their blue continuum and broad line emission are classified as changing-look AGN, or at higher luminosities, changing-look quasars (CLQs).
C. MacLeod +17 more
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Gemini GNIRS Near-infrared Spectroscopy of 50 Quasars at z ≳ 5.7 [PDF]
Astrophysical Journal, 2018 We report initial results from a large Gemini program to observe z ≳ 5.7 quasars with GNIRS near-IR spectroscopy. Our sample includes 50 quasars with simultaneous ∼0.85–2.5 μm spectra covering the rest-frame ultraviolet and major broad emission lines ...
Yue Shen +14 more
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Some Constraints on Quasar Progenitors and Quasar Evolution [PDF]
Symposium - International Astronomical Union, 1986 There is strong evidence that quasars are powered by the gravitational energy released by in fall of matter into a compact supermassive object which is most likely a black hole with mass M>106 to 109MO. The question then arises as to how such massive black holes came to be formed. What sort of objects were the progenitors?
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Gaia Space Mission and Quasars
Frontiers in Astronomy and Space Sciences, 2017 Quasars are often considered to be point-like objects. This is largely true and allows for an excellent alignment of the optical positional reference frame of the ongoing ESA mission Gaia with the International Celestial Reference Frame.
Tomaž Zwitter
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The Astrophysical Journal, 2023 We explore reprocessing models for a sample of 17 hypervariable quasars, taken from the Sloan Digital Sky Survey Reverberation Mapping project, which all show coordinated optical luminosity hypervariability with amplitudes of factors ≳2 between 2014 and ...
Tatsuya Akiba +7 more
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