Results from Five Years of Monitoring of the Einstein Cross with Not

Østensen, R. H.; Refsdal, S.; Stabell, R.; Teuber, J.

doi:10.1007/978-94-009-0221-3_69

Cited by 20 publications

(22 citation statements)

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“…Photometric monitoring revealed uncorrelated variability between the various images, interpreted as being due to gravitational microlensing (Irwin et al 1989). This interpretation was confirmed with dedicated monitoring programs (e.g., Østensen et al 1996;Woźniak et al 2000a,b;Alcalde et al 2002). Q2237+0305 is the best studied quasar microlensing system.…”

Section: Introductionmentioning

confidence: 70%

Limits on the transverse velocity of the lensing galaxy in Q2237+0305 from the lack of strong microlensing variability

Gil-Merino

Wambsganß

Goicoechea

et al. 2005

A&A

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Abstract. We present a method for the determination of upper limits on the transverse velocity of the lensing galaxy in the quadruple quasar system Q2237+0305, based on the lack of strong microlensing signatures in the quasar lightcurves. The limits we derive here are based on four months of high quality monitoring data, by comparing the low amplitudes of the lightcurves of the four components with extensive numerical simulations. We make use of the absence of strong variability of the components (especially components B and D) to infer that a "flat" time interval of such a length is only compatible with an effective transverse velocity of the lensing galaxy of v bulk ≤ 630 km s −1 for typical microlenses masses of M µlens = 0.1 M (or v bulk ≤ 2160 km s −1 for M µlens = 1.0 M ) at the 90% confidence level. This method may be applicable in the future to other systems.

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Section: Introductionmentioning

confidence: 70%

Limits on the transverse velocity of the lensing galaxy in Q2237+0305 from the lack of strong microlensing variability

Gil-Merino

Wambsganß

Goicoechea

et al. 2005

A&A

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“…We have already analyzed the behavior of the relative colors of the Q2237+0305 components qualitatively (Dudinov et al 2000a,b), based upon our observations at Maidanak in 1995 (Vakulik et al 1997(Vakulik et al ), and in 1997(Vakulik et al −1998, and also upon all available multicolor observations by other authors (Burud et al 1998;Østensen et al 1996;Rix et al 1992;Yee 1988). A tendency for the components to become bluer as their brightness increases was noted there, but no quantitative relationships were derived.…”

Section: Variations Of Color In Q2237+0305mentioning

confidence: 96%

Color effects associated with the 1999 microlensing brightness peaks in gravitationally lensed quasar Q2237+0305

Vakulik¹,

Schild

Dudinov³

et al. 2004

A&A

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Abstract. We present photometry of the Q2237+0305 gravitational lens system in VRI spectral bands with the 1.5-m telescope of the high-altitude Maidanak observatory in 1995−2000. The time interval includes the epoch of the dramatic brightness peaks discovered previously in the A and C image components (Wozniak et al. 2000a,b). By good luck three nights of observation in 1999 were almost at the time of the strong brightness peak of image C, and approximately in the middle of the ascending slope of the brightness peak of image A. Having reached its brightness maximum at the very end of June 1999, the C component had changed its (V − I) color from 0.3 m to 0.12 m since August 1998, and from 0.56 m to 0.12 m since August 1997. It was the bluest component in the system in 1998 and 1999, but by October 2000 that was no longer the case. We do not know the color of the A component exactly at its brightness peak, but we do know that it became 0.47 m brighter in R and 0.15 m bluer in (V − R) between August 1998 and August 2000, about three months before the peak. More intensive monitoring of Q2237+0305 in July-October 2000, made on a nearly daily basis, did not reveal rapid (night-to-night and intranight) brightness variations of the components during this time period, exceeding the photometry error bars. Rather slow changes of magnitudes of the components were observed, in particular, nearly synchronous 0.08 m fading of B and C components, and 0.05 m brightening of D in the R band during July 23−October 7, 2000, while the B component had become the faintest in all filters by the end of this time period. The behavior of the colors of the components was analyzed on the basis of all our VRI observations, made in 1995−2000 on Maidanak. A qualitative tendency of the components to become bluer as their brightness increases, noted in our previous works, was confirmed quantitatively. A correlation between the color variations and variations of magnitudes of the components is demonstrated to be significant and reaches 0.75 for ∆(V − I) vs. ∆R, with a regression line slope of 0.33± 0.08 for these quantities. A plot of (V − I) vs. (V − R) shows the components settled in a cluster, stretchng along a line with a slope of 1.31 ± 0.14. Both slopes are noticeably less steep than those expected if a standard galactic interstellar reddening law were responsible for the differences between the colors of images and their variations over time. We attribute the brightness and color changes to microlensing of the quasar's structure, which we conclude to be more compact at shorter wavelengths, as predicted by most quasar models featuring an energizing central source.

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“…Absolute photometry of the four lensed QSO components of Q2237+0305 was performed in each band using the so-called General software (Remy 1996;Østensen et al 1996). We fitted the central part of both the V and R reference frames Ref with a global model of the gravitational lens system composed of one PSF for each of the four lensed components plus a model for the lensing galaxy photometric profile.…”

Section: Modeling Q2237+0305 On the Reference Framementioning

confidence: 99%

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

Libbrecht

Lee

et al. 2005

A&A

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Abstract.Using an optimal image subtraction technique, we have derived the V and R light curves of the four lensed QSO components of Q2237+0305 from the monitoring CCD frames obtained by the GLITP collaboration with the 2.6 m NOT telescope in 1999/2000 . We give here a detailed account of the data reduction and analysis and of the error estimates. In agreement with Woźniak et al. (2000a,b), the good derived photometric accuracy of the GLITP data allows to discuss the possible interpretation of the light curve of component A as due to a microlensing event taking place in the deflecting galaxy. This interpretation is strengthened by the colour dependence of the early rise of the light curve of component A, as it probably corresponds to a caustics crossing by the QSO source.

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Results from Five Years of Monitoring of the Einstein Cross with Not

Cited by 20 publications

References 1 publication

Limits on the transverse velocity of the lensing galaxy in Q2237+0305 from the lack of strong microlensing variability

Limits on the transverse velocity of the lensing galaxy in Q2237+0305 from the lack of strong microlensing variability

Color effects associated with the 1999 microlensing brightness peaks in gravitationally lensed quasar Q2237+0305

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

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