scholarly journals Time delay of critical images in the vicinity of cusp point of gravitational-lens systems

2016 ◽  
Vol 54 (2) ◽  
pp. 41-46
Author(s):  
A. Alexandrov ◽  
◽  
V. Zhdanov ◽  
Keyword(s):  
Time Delay ◽  
Gravitational Lens ◽  
Cusp Point

scholarly journals Ambiguities in gravitational lens models: impact on time delays of the source position transformation

2018 ◽  
Vol 617 ◽  
pp. A140 ◽  
Author(s):  
Olivier Wertz ◽  
Bastian Orthen ◽  
Peter Schneider
Keyword(s):  
Time Delay ◽  
Time Delays ◽  
Hubble Constant ◽  
Companion Paper ◽  
Gravitational Lens ◽  
Source Position ◽  
Double Image ◽  
Validity Criterion ◽  
Mass Profile ◽  
Image Pairs

The central ambition of the modern time delay cosmography consists in determining the Hubble constant H0 with a competitive precision. However, the tension with H0 obtained from the Planck satellite for a spatially flat ΛCDM cosmology suggests that systematic errors may have been underestimated. The most critical of these errors probably comes from the degeneracy existing between lens models that was first formalized by the well-known mass-sheet transformation (MST). In this paper, we assess to what extent the source position transformation (SPT), a more general invariance transformation which contains the MST as a special case, may affect the time delays predicted by a model. To this aim, we have used pySPT, a new open-source python package fully dedicated to the SPT that we present in a companion paper. For axisymmetric lenses, we find that the time delay ratios between a model and its SPT-modified counterpart simply scale like the corresponding source position ratios, Δtˆ/Δt ≈ βˆ/β, regardless of the mass profile and the isotropic SPT. Similar behavior (almost) holds for nonaxisymmetric lenses in the double image regime and for opposite image pairs in the quadruple image regime. In the latter regime, we also confirm that the time delay ratios are not conserved. In addition to the MST effects, the SPT-modified time delays deviate in general no more than a few percent for particular image pairs, suggesting that its impact on time delay cosmography seems not be as crucial as initially suspected. We also reflected upon the relevance of the SPT validity criterion and present arguments suggesting that it should be reconsidered. Even though a new validity criterion would affect the time delays in a different way, we expect from numerical simulations that our conclusions will remain unchanged.

scholarly journals Can We Measure H0 with VLBI Observations of Gravitational Images?

1988 ◽  
Vol 129 ◽  
pp. 207-208
Author(s):  
E. E. Falco ◽  
M. V. Gorenstein ◽  
I. I. Shapiro
Keyword(s):  
Time Delay ◽  
Mass Distribution ◽  
Velocity Dispersion ◽  
Gravitational Lens ◽  
Lens System ◽  
Relative Time ◽  
Surface Mass ◽  
A Value ◽  
Vlbi Observations ◽  
The Difference

We have used the relative positions and magnifications of the A and B images in the gravitational lens system 0957+561, obtained from VLBI observations, to constrain a model for the surface mass distribution of the lens. With measurements of the difference ΔτBA in propagation times associated with A and B (the “relative time delay”) and of the velocity dispersion of the main lensing galaxy, both to be obtained, our model will yield a value for H0 with an uncertainty of ∼ 20% due mainly to uncertainties in our assumptions.

The Time Delay of Gravitational Lens 0957+561. II. Analysis of Radio Data and Combined Optical-Radio Analysis

1992 ◽  
Vol 385 ◽  
pp. 416 ◽  
Author(s):  
William H. Press ◽  
George B. Rybicki ◽  
Jacqueline N. Hewitt
Keyword(s):  
Time Delay ◽  
Gravitational Lens ◽  
Radio Data

scholarly journals Gravitational time delay of signals in the Kerr metric

1986 ◽  
Vol 114 ◽  
pp. 411-416
Author(s):  
I. G. Dymnikova
Keyword(s):  
Time Delay ◽  
Strong Field ◽  
Rotation Axis ◽  
Wave Length ◽  
Field Approximation ◽  
Weak Field ◽  
Gravitational Lens ◽  
Mutual Orientation ◽  
Kerr Metric ◽  
Photon Propagation

The gravitational time delay of signals in a gravitational field of a rotating massive body is considered both in a weak field approximation and in a strong field caused by a rotating black hole. The expressions describing the time of propagation of signals are obtained by integrating the light geodesics of the Kerr metric in a frame reference of a distant observer using the Boyer-Lindquist coordinates and assuming that the wave length of radiation is much less than the characteristic scale of the field. The existence of the asymmetry in the time delay is shown depending on the mutual orientation of a photon propagation direction and of the rotation axis. As a result of this asymmetry, the effects of relative time delay are predicted and calculated for the signals focused by a rotating gravitational lens.

scholarly journals Photometric Monitoring Of The Lensed QSO 0957+561

1996 ◽  
Vol 173 ◽  
pp. 53-54
Author(s):  
D. Sinachopoulos ◽  
M. Burger ◽  
E. van Dessel ◽  
M. Geffert ◽  
M. Thibor ◽  
...  
Keyword(s):  
Time Delay ◽  
Gravitational Lens ◽  
Large Field ◽  
Photometric Study ◽  
First Results ◽  
Photometric Monitoring

We present our first results of a photometric monitoring project of the twin quasar 0957+561. This project aims mainly at the improvement of the determination of the time delay ΔT(A,B) for this gravitational lens, since the “time delay controversy on QSO 0957+561 (is) not yet decided” (Pelt et al. 1994). In addition, the quite large field of the CCD used allows also a long-term astrometric and photometric study of stars and galaxies in the field within a radius of about 10 arcminutes around the lens.

scholarly journals Gravitational Lenses and VLBI Structures

1984 ◽  
Vol 110 ◽  
pp. 249-250
Author(s):  
K. Subramanian ◽  
D. Narasimha ◽  
S. M. Chitre
Keyword(s):  
Time Delay ◽  
Elliptical Galaxy ◽  
Gravitational Lens ◽  
Gravitational Lenses ◽  
Low Mass Stars ◽  
Effective Time ◽  
Low Mass ◽  
Intensity Fluctuations

The double quasar 00957 + 561 A,B along with bright radio arches and VLBI structures is modelled using a gravitational lens consisting of an elliptical galaxy and a cluster. The effective time-delay between components A and B comes out to be about a year and this enables one to distinguish between intensity fluctuations resulting from intrinsic quasar variations and minilensing by low mass stars.

scholarly journals LONG-TERM MONITORING, TIME DELAY, AND MICROLENSING IN THE GRAVITATIONAL LENS SYSTEM Q0142-100

2013 ◽  
Vol 779 (2) ◽  
pp. 144 ◽  
Author(s):  
A. Oscoz ◽  
M. Serra-Ricart ◽  
E. Mediavilla ◽  
J. A. Muñoz
Keyword(s):  
Time Delay ◽  
Gravitational Lens ◽  
Lens System ◽  
Monitoring Time ◽  
Long Term Monitoring ◽  
Term Monitoring

Gravitational Lensing for Measuring Astrophysical Quantities

2005 ◽  
Vol 277-279 ◽  
pp. 783-788
Author(s):  
K. Chang
Keyword(s):  
Time Delay ◽  
Gravitational Lensing ◽  
Critical Curve ◽  
Gravitational Lens ◽  
Density Parameter ◽  
Cosmological Distance Scale ◽  
Compact Source ◽  
Cosmological Distance ◽  
Structure Density ◽  
Source Structure

Gravitational lensing (GL) provides the sudden changes in flux densities, when a compact source crosses a critical curve. Due to lensing, the image of the lensed object is split into at least two images, and merged together upon the source crossing the critical curve. Light paths of the images differ from one another’s, so results time delay to the observer. Asymmetric light curves and the time delay in lensing contain astrophysical information on the GL system: e.g. source structure, density distribution, and cosmological distance scale. The disalignment of GL system, b, is an important parameter in the GL analysis. We derive b as a function of density parameter of gravitational lens mass. We present an analytical formulation to determine cosmological distance scales, hence the Hubble parameter, and other properties of GL system. We also discuss degeneracies in the GL mapping.

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