Image reconstruction technique and optical monitoring of the QSO2237+0305 from Maidanak Observatory in 2002-2003

Koptelova, E.; Shimanovskaya, E. V.; Артамонов, Б. П.; Sazhin, M. V.; Yagola, A. G.; Bruevich, V. V.; Burkhonov, O.

doi:10.1111/j.1365-2966.2004.08451.x

Cited by 27 publications

(22 citation statements)

References 22 publications

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“…2 (see Table 2), that the light curves of all the components are highly correlated, both in the R filter (our observations), and in the V band (OGLE data). It should be noted however that the R light curves built from the same Maidanak data by the Moscow group, (Koptelova et al 2005) differ from our light curves, with the cross correlation indices being much lower than those shown in Table 2, and ranging from 0.2 to 0.7. If the light curves observed during the time period from June 27 to October 12, 2003, represent a quasar intrinsic brightness change, then its amplitude seen in different lensed images is believed to be the same.…”

Section: Quasar Intrinsic Brightness Fluctuation Amplitudecontrasting

confidence: 85%

Observational determination of the time delays in gravitational lens system Q2237+0305

Vakulik¹,

Schild

Dudinov³

et al. 2006

A&A

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We present new brightness monitoring observations of the 4 components of gravitationally lensed system Q2237+0305, which show detection of an intrinsic quasar brightness fluctuation at a time of subdued microlensing activity, between June 27 and October 12, 2003. These data were used to determine the time delays between the arrivals of the four images. The measured delays are τ BA ≈ −6, τ CA ≈ 35, and τ DA ≈ 2 h, so they confirm that the long history of brightness monitoring has produced significant detection of microlensing. However the error bars associated with the delays, of order 2 days, are too large to discriminate between competing macro-imaging models. Moreover, our simulations show that for the amplitude of this intrinsic fluctuation and for photometric errors intrinsic to optical monitoring from our 1.5-m telescope or from the OGLE monitoring, a daily sampled brightness record cannot produce reliable lags for model discrimination. We use our simulations to devise a strategy for future delay determination with optical data. Nevertheless, we regard these first estimates to be significant, since they are the first direct measurements of time delays made for this system from ground-based observations in the visual wavelengths. The detected highly correlated fluctuations of the four quasar images provide an extra confirmation of the gravitational-lens nature of Q2237+0305, and give observational justification to the extensive literature which attributes the quasar's previously observed brightness fluctuations to microlensing.

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Section: Quasar Intrinsic Brightness Fluctuation Amplitudecontrasting

confidence: 85%

Observational determination of the time delays in gravitational lens system Q2237+0305

Vakulik¹,

Schild

Dudinov³

et al. 2006

A&A

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“…Stetson, Davis & Crabtree 1990;Magain, Courbin & Sohy 1998;Lupton et al 2001;Koptelova et al 2005). The majority of these methods requires the assumption of PSF invariance over the frame.…”

Section: T H E a Da P T I V E P S F -F I T T I N G P H Oto M E T R I mentioning

confidence: 99%

Adaptive PSF fitting – a highly performing photometric method and light curves of the GLS H1413+117: time delays and micro-lensing effects

Akhunov

Wertz

Elyiv

et al. 2016

Mon. Not. R. Astron. Soc.

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We present new photometric observations of H1413+117 acquired during seasons between 2001 and 2008 in order to estimate the time delays between the lensed quasar images and to characterize at best the on-going micro-lensing events. We propose a highly performing photometric method called the adaptive point spread function fitting and have successfully tested this method on a large number of simulated frames. This has enabled us to estimate the photometric error bars affecting our observational results. We analysed the V-and R-band light curves and V-R colour variations of the A-D components which show short-and long-term brightness variations correlated with colour variations. Using the χ 2 and dispersion methods, we estimated the time delays on the basis of the R-band light curves over the seasons between 2003 and 2006. We have derived the new values: t AB = −17.4 ± 2.1, t AC = −18.9 ± 2.8 and t AD = 28.8 ± 0.7 d using the χ 2 method (B and C are leading, D is trailing) with 1σ confidence intervals. We also used available observational constraints (resp. the lensed image positions, the flux ratios in mid-IR and two sets of time delays derived in the present work) to update the lens redshift estimation. We obtained z l = 1.95 +0.06 −0.10 which is in good agreement with previous estimations. We propose to characterize two kinds of micro-lensing events: micro-lensing for the A,

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“…1 we show system subframes (left panels), model subframes (middle panels), and residual subframes (right panels) corresponding to five frames in the g band. To check the reliability of our PSF fitting procedure, we applied a deconvolution technique (Koptelova et al 2005) to two sets of frames in October-December 2005 (gr bands). The relative instrumental magnitudes from the deconvolution method agreed with the records from the PSF fitting technique (see Fig.…”

Section: Instrumental Photometrymentioning

confidence: 99%

New two-colour light curves of Q0957+561: time delays and the origin of intrinsic variations

Shalyapin¹,

Goicoechea²,

Koptelova³

et al. 2008

A&A

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Aims. We extend the gr-band time coverage of the gravitationally lensed double quasar Q0957+561. New gr light curves permit us to detect significant intrinsic fluctuations, to determine new time delays, and thus to gain perspective on the mechanism of intrinsic variability in Q0957+561. Methods. We use new optical frames of Q0957+561 in the g and r passbands from January 2005 to July 2007. These frames are part of an ongoing long-term monitoring with the Liverpool robotic telescope. We also introduce two photometric pipelines that are applied to the new gr frames of Q0957+561. The transformation pipeline incorporates zero-point, colour, and inhomogeneity corrections to the instrumental magnitudes, so final photometry to the 1-2% level is achieved for both quasar components. The two-colour final records are then used to measure time delays. Results. The gr light curves of Q0957+561 show several prominent events and gradients, and some of them (in the g band) lead to a time delay between components Δt BA = 417 ± 2 d (1σ). We do not find evidence of extrinsic variability in the light curves of Q0957+561. We also explore the possibility of a delay between a large event in the g band and the corresponding event in the r band. The gr cross-correlation reveals a time lag Δt rg = 4.0 ± 2.0 d (1σ; the g-band event is leading) that confirms a previous claim of the existence of a delay between the g and r band in this lensed quasar. Conclusions. The time delays (between quasar components and between optical bands) from the new records and previous ones in similar bands indicate that most observed variations in Q0957+561 (amplitudes of ∼100 mmag and timescales of ∼100 d) are very probably due to reverberation within the gas disc around the supermassive black hole.

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Image reconstruction technique and optical monitoring of the QSO2237+0305 from Maidanak Observatory in 2002-2003

Cited by 27 publications

References 22 publications

Observational determination of the time delays in gravitational lens system Q2237+0305

Observational determination of the time delays in gravitational lens system Q2237+0305

Adaptive PSF fitting – a highly performing photometric method and light curves of the GLS H1413+117: time delays and micro-lensing effects

New two-colour light curves of Q0957+561: time delays and the origin of intrinsic variations

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