Accurate photometric light curves of the lensed components  
of Q2237+0305 derived with an optimal image subtraction technique: Evidence for microlensing in image A

Moreau, O.; Libbrecht, C.; Lee, D. W.; Surdej, Jean

doi:10.1051/0004-6361:20041887

Cited by 8 publications

(9 citation statements)

References 18 publications

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“…In this system, significant microlensing‐induced brightness peaks on light curves of the quasar images were detected (see, e.g. Wozńiak et al 2000; Alcalde et al 2002; Moreau et al 2005).…”

Section: Hae In the Einstein Crossmentioning

confidence: 97%

Asymptotic expansions and amplification of a gravitational lens near a fold caustic

Alexandrov¹,

Жданов²

2011

Monthly Notices of the Royal Astronomical Society

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We propose two methods that enable us to obtain approximate solutions of the lens equation near a fold caustic with an arbitrary degree of accuracy. We obtain ‘post‐linear’ corrections to the well‐known formula in the linear caustic approximation for the total amplification of two critical images of a point source. In this case, in order to obtain the non‐trivial corrections we have to go beyond the approximation orders earlier used by Keeton et al. and to perform the Taylor expansion of the lens equation near the caustic up to the fourth order. Corresponding analytical expressions are derived for the amplification in cases of the Gaussian and power‐law extended source models; the amplifications depend on three additional fitting parameters. Conditions of neglecting the correction terms are analysed. The modified formula for the amplification is applied to the fitting of light curves of the Q2237+0305 gravitational lens system in the vicinity of the high amplification events (HAEs). We show that the introduction of some ‘post‐linear’ corrections reduces χ2 by 30 per cent in the case of known HAE on the light curve of image C (1999). These corrections can be important for a precise comparison of different source models with regard for observational data.

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Section: Hae In the Einstein Crossmentioning

confidence: 97%

Asymptotic expansions and amplification of a gravitational lens near a fold caustic

Alexandrov¹,

Жданов²

2011

Monthly Notices of the Royal Astronomical Society

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“…We note that the colours of the object have been shown to vary with time (Moreau et al 2005) and therefore there must be an effect, in addition to or instead of dust extinction, affecting the colours, for example microlensing. This would explain why we derive best-fit values for R V that are unrealistically low, and why completely different values have been obtained using other data sets.…”

Section: Specific Systemsmentioning

confidence: 99%

Extinction properties of lensing galaxies

Östman

Goobar

Mörtsell

2008

A&A

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Context. Observations of quasars shining through foreground galaxies, offer a way to probe the dust extinction curves of distant galaxies. Interesting objects for this study are found in strong gravitational lensing systems, where the foreground galaxies generate multiple images. Aims. The reddening law of lensing galaxies is investigated by studying the colours of gravitationally-lensed quasars, and a handful of other quasars where a foreground galaxy is detected. Methods. We compare the observed colours of quasars reported in the literature, with spectral templates reddened by different extinction laws and dust properties. The data consists of 21 quasar-galaxy systems, with a total of 48 images. The galaxies, which are both early-and late-type, have redshifts in the interval z = 0.04−1.51. Results. We measure a difference in rest-frame B − V between the quasar images we study, and quasars without resolved foreground galaxies. This difference in colour is indicative of significant dust extinction in the intervening galaxy. Good fits to standard extinction laws were found for 22 of the images, corresponding to 13 different galaxies. Our fits imply a wide range of possible values for the total-to-selective extinction ratio, R V . The distribution was found to be broad with a weighted mode ofR V = 2.4 and a FWHM of ΔR V = 2.7 (σ R V ∼ 1.1). Thus the bulk of the galaxies for which good reddening fits could be derived, have dust properties compatible with the Milky Way value (R V = 3.1).

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“…It has been continuously monitored by a number of groups from 1992-2005 (Rix et al 1992;Falco et al 1996;Oestensen et al 1996;Blanton et al 1998;Bliokh et al 1999;Nadeau et al 1999;Wozniak et al 2000;Alcalde et al 2002;Schmidt et al 2002). Significant microlensing-induced brightness peaks on lightcurves of quasar images were detected in this system (see, e.g., Wozniak et al 2000;Alcalde et al 2002;Moreau et al 2005). The OGLE group is continuing observations of the Einstein Cross and the database http://bulge.princeton.edu/~ogle is being constantly renewed.…”

Section: Introductionmentioning

confidence: 99%

Q2237+0305 in X-rays: spectra and variability with XMM-Newton

Fedorova

Жданов

Vignali

et al. 2008

A&A

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Aims. X-ray observations of gravitationally lensed quasars may allow us to probe the inner structure of the central engine of a quasar. Observations of Q2237+0305 (Einstein Cross) in X-rays may be used to constrain the inner structure of the X-ray emitting source. Methods. Here we analyze the XMM-Newton observation of the quasar in the gravitational lens system Q2237+0305 taken during 2002. Combined spectra of the four images of the quasar in this system were extracted and modelled with a power-law model. Statistical analysis was used to test the variability of the total flux. Results. The total X-ray flux from all the images of this quadruple gravitational lens system is 6 × 10 −13 erg/(cm 2 s) in the range 0.2-10 keV, showing no significant X-ray spectral variability during almost 42 ks of the observation time. Fitting of the cleaned source spectrum yields a photon power-law index of Γ = 1.82−0.08 . The X-ray lightcurves obtained after background subtraction are compatible with the hypothesis of a stationary flux from the source.

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Accurate photometric light curves of the lensed components of Q2237+0305 derived with an optimal image subtraction technique: Evidence for microlensing in image A

Cited by 8 publications

References 18 publications

Asymptotic expansions and amplification of a gravitational lens near a fold caustic

Asymptotic expansions and amplification of a gravitational lens near a fold caustic

Extinction properties of lensing galaxies

Q2237+0305 in X-rays: spectra and variability with XMM-Newton

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