Flux variations of QSO 0957 + 561 A, B and image splitting by stars near the light path

Chang, Kyongae; Refsdal, S.

doi:10.1038/282561a0

Cited by 419 publications

(337 citation statements)

References 13 publications

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“…Microlensing can change the results by about 0.5−1.0 mag and it is completely unpredictable (Chang & Refsdal 1979).…”

Section: Observationmentioning

confidence: 99%

“…Based on our modeling (G1 -SIE and G3 -SIS) (see Sect. 8) and Chang & Refsdal (1979) predicted that in lensed quasar systems the light path should be affected by stars in the lensing galaxy. Moving compact objects in the lensing galaxy can cause spectral changes, brightness variability and, in the case of multiple images, flux-ratio anomalies in the lensed quasar.…”

Section: Time Delay Of Sdss J1206+4332mentioning

confidence: 99%

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Results of optical monitoring of 5 SDSS double QSOs with the Nordic Optical Telescope

Paraficz¹,

Hjorth²,

Elíasdóttir

2009

A&A

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We present optical R-band light curves of five SDSS double QSOs (SDSS J0903+5028, SDSS J1001+5027, SDSS J1206+4332, SDSS J1353+1138, SDSS J1335+0118) obtained from monitoring at the Nordic Optical Telescope (NOT) between September 2005 and September 2007. We also present analytical and pixelated modeling of the observed systems. For SDSS J1206+4332, we measured the time delay to be Δτ = 116 +4 −5 days, which, for a singular isothermal ellipsoid model, corresponds to a Hubble constant of 73 +3 −4 km s −1 Mpc −1 . Simultaneous pixelated modeling of five other systems for which a time delay has now been previously measured at the NOT leads to H 0 = 61.5 +8 −4 km s −1 Mpc −1 . Finally, by comparing light curves of the two images of each system, suitably shifted by the predicted or observed time-delays, we found no evidence of microlensing variability over the course of the monitoring period.

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“…Microlensing can change the results by about 0.5−1.0 mag and it is completely unpredictable (Chang & Refsdal 1979).…”

Section: Observationmentioning

confidence: 99%

Section: Time Delay Of Sdss J1206+4332mentioning

confidence: 99%

Results of optical monitoring of 5 SDSS double QSOs with the Nordic Optical Telescope

Paraficz¹,

Hjorth²,

Elíasdóttir

2009

A&A

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show abstract

“…Gravitational microlensing (Chang & Refsdal 1979, 1984; see also Kochanek 2004 andWambsganss 2006) is the main tool used to estimate both parameters, either from time variability or through the wavelength dependence of the microlensing magnification. Microlensing studies (see e.g., Pooley et al 2007;Morgan et al 2010;Blackburne et al 2011Blackburne et al , 2014Blackburne et al , 2015Sluse et al 2011;Jiménez-Vicente et al 2012Hainline et al 2013;Mosquera et al 2013;MacLeod et al 2015) have found that the mean sizes of quasar accretion disks are roughly a factor of 2-3 greater than the predictions of the standard thin disk model.…”

Section: Introductionmentioning

confidence: 99%

Structure of the Accretion Disk in the Lensed Quasar Q2237+0305 From Multi-Epoch and Multi-Wavelength Narrowband Photometry

Muñoz

Vives-Arias

Mosquera

et al. 2016

ApJ

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We present estimates for the size and the logarithmic slope of the disk temperature profile of the lensed quasar Q2237+0305, independent of the component velocities. These estimates are based on six epochs of multiwavelength narrowband images from the Nordic Optical Telescope. For each pair of lensed images and each photometric band, we determine the microlensing amplitude and chromaticity using pre-existing mid-IR photometry to define the baseline for no microlensing magnification. A statistical comparison of the combined microlensing data (6 epochs×5 narrow bands×6 image pairs) with simulations based on microlensing magnification maps gives Bayesian estimates for the half-light radius oflt-day, and p=0.95±0.33 for the exponent of the logarithmic temperature profile µ -T R p 1 . This size estimate is in good agreement with most recent studies. Other works based on the study of single microlensing events predict smaller sizes, but could be statistically biased by focusing on high-magnification events.

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“…Cosmological microlensing was Ðrst discussed by Chang & Refsdal (1979), Gott (1981), and Young (1981), who pointed out that the relative motion between stars in other galaxies and background sources should cause variability in the observed Ñux, providing an avenue to investigate an otherwise inaccessible mass regime. This phenomenon was subsequently observed in the quadruple gravitational lens Q2237]0305 (Irwin et al 1989 ;Corrigan et al 1991).…”

Section: Introductionmentioning

confidence: 99%

On the Probability Distribution of Cosmological Microlensing Optical Depths

Wyithe¹,

Turner²

2002

ApJ

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It is conventional to calculate the probability of microlensing for a cosmologically distant source based on the Press-Gunn approximation that the lensing objects are uniformly and randomly distributed in the intervening space with a constant comoving density. We here investigate more realistic cosmological microlensing statistics by considering the strong spatial clustering of likely lensing objects with each other in galaxies and their association with the clumps of dark matter that make up the massive halos of galaxies. Both cases in which microlensing objects are distributed like the observed starlight in galaxies and ones in which the extended massive halos themselves are also composed of compact massive objects capable of acting as microlenses are investigated. The distribution of microlensing optical depth i along randomly chosen sight lines is calculated, as is the conditional distribution of i along sight lines near one that is strongly microlensed. Illustrative magniÐcation biases are also considered. These distributions allow us to calculate both the probability that a high-redshift source will be microlensed in the various scenarios and the likely local i (averaged over nearby sight lines) at which such microlensing events will occur. Our overall result is that the Press-Gunn approximation is a useful order-of-magnitude approximation if the massive halos of galaxies are made of dark compact objects, but that it fails badly and can be qualitatively misleading in the more likely case in which only the ordinary stellar populations of galaxies are the dominant source of cosmological microlensing events. In particular, we Ðnd that microlensing by stars is limited to of the order of 1% of high-redshift sources at any one time. Furthermore, even though only a small fraction of high-redshift sources are multiply imaged (by galaxies), it is these sources that are most likely to be microlensed by stars. Consequently, microlensing by stars is usually observed at i near 1 where the simple isolated point mass lens approximation is not appropriate. However, if cold dark matter halos are composed of condensed objects, then more than 10% of high-redshift sources are microlensed at any given time. The vast majority of these sources are not multiply imaged, and have i smaller than 0.01.

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Flux variations of QSO 0957 + 561 A, B and image splitting by stars near the light path

Cited by 419 publications

References 13 publications

Results of optical monitoring of 5 SDSS double QSOs with the Nordic Optical Telescope

Results of optical monitoring of 5 SDSS double QSOs with the Nordic Optical Telescope

Structure of the Accretion Disk in the Lensed Quasar Q2237+0305 From Multi-Epoch and Multi-Wavelength Narrowband Photometry

On the Probability Distribution of Cosmological Microlensing Optical Depths

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