ESO &amp; NOT photometric monitoring of the Cloverleaf
quasar

Østensen, R. H.; Rémy, M.; Lindblad, P. O.; Refsdal, S.; Stabell, R.; Surdej, Jean; Barthel, P. D.; Emanuelsen, P. I.; Festin, L.; Gosset, Éric; Hainaut, O.; Hakala, Pasi; Hjelm, M.; Hjorth, J.; Hutsemékers, Damien; Jablonski, M.; Kaas, A. A.; Kristen, H.; Larsson, Stefan; Magain, Pierre; Pettersson, Bertil; Pospieszalska-Surdej, Anna; Smette, A.; Teuber, J.; Thomsen, B.; Drom, E. van

doi:10.1051/aas:1997273

Cited by 23 publications

(17 citation statements)

References 7 publications

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“…Our results are in good agreement with those published previously by Goodrich & Miller (1995), Schmidt & Hines (1999) and Ogle et al (1999), despite of the fact that the total flux and the polarization of B1413+1143 are known to be variable (e.g. Goodrich & Miller 1995;Østensen et al 1997).…”

Section: Description Of Individual Objectssupporting

confidence: 93%

Polarization properties of broad absorption line QSOs: New statistical clues

Lamy

Hutsemékers

2004

A&A

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Abstract.We report the results of several statistical tests performed on a large sample of 139 broad absorption line (BAL) QSOs with good quality optical spectra and/or optical polarization data. Correlations between ten optical indices and the polarization degree p 0 are systematically searched for. We find six significant non-trivial correlations. In order to identify the most important correlations, we perform a principal component analysis with a sample of 30 BAL QSOs and eight quantities (including p 0 ). Most of the variance (∼57%) in the data is contained in two principal components called PC1 and PC2. PC1 is mainly dominated by the correlation between the balnicity index BI and the strength of the Fe  emission; it may be driven by the accretion rate of matter onto the central compact object. The variance in PC2 is essentially due to the anti-correlation between p 0 and the detachment index DI, indicating that BAL QSOs with P Cygni profiles (DI ) are usually more polarized than those objects with C  absorption troughs well detached from the corresponding emission lines (DI ). We show that PC2 may be related to the orientation of the BAL QSOs with respect to the line of sight. We also present new spectropolarimetric observations of six BAL QSOs. By adding spectropolarimetric data from the literature, we build a sample of 21 BAL QSOs for which we define four spectropolarimetric indices describing the polarization properties of the absorption and emission lines. We find that the polarization of the C ] emission line is systematically higher than the polarization of the C  emission line, and that the highest polarization in the troughs is correlated to the balnicity index. Another important result emerging from the statistical tests performed on this spectropolarimetric sample is a possible anti-correlation between the detachment index and a quantity SI which measures the ratio of the depths of the C  absorption in the polarized flux and in the total flux. This correlation indicates that in BAL QSOs with P cygni profiles, the BAL troughs in the polarized flux are nearly as deep as in the total flux while, in BAL QSOs with detached absorptions, the BAL troughs in the polarized flux are much weaker than in the total flux. We show that our main results may be explained in the framework of a "two-component" wind model which is a natural extension of the classical wind-from-disk models. In this model, the broad absorption occurs in a dense equatorial wind emerging from the accretion disk, while scattering and polarization mainly take place in a polar region. The orientation relative to the observer drives the correlations p 0 -DI and DI -SI. While most of our observations can be explained within this framework, there are also several indications that other polarization mechanisms, and more particularly resonance scattering, may also be at work.

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Section: Description Of Individual Objectssupporting

confidence: 93%

Polarization properties of broad absorption line QSOs: New statistical clues

Lamy

Hutsemékers

2004

A&A

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“…These differences are not seen any longer in the VIMOS dataset, which again is a result favoring microlensing in image D, as 15 years is roughly the expected timescale for microlensing variations in H 1413+117 (Hutsemekers 1993). Finally, Ostensen et al (1997) have shown, from their photometric monitoring between 1987 and 1995, almost parallel light curves for the quasar images, except for image D. Image D exhibits a slightly higher amplitude in its overall variation, which, added to its spectral differences, makes a strong case for additional microlensing affecting image D. -Intrinsic variability: intrinsic variations of the quasar flux coupled with time-delays between its multiple images would also induce spectral differences between the images. Timedelays for this quasar have not been measured yet.…”

Section: Spectral Differences In H 1413+117mentioning

confidence: 88%

Integral field spectroscopy of four lensed quasars: analysis of their neighborhood and evidence for microlensing

Anguita¹,

Fauré²,

Yonehara³

et al. 2008

A&A

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Context. Gravitationally lensed quasars constitute an independent tool to derive the Hubble constant through the time-delays of their different images; they offer as well the opportunity to study the mass distribution and interstellar medium of their lensing galaxies and, through microlensing due to stars in their lensing galaxy, they also allow one to study details of the emitting source. Aims. For such studies, one needs to have an excellent knowledge of the close environment of the lensed images in order to model the lensing potential: this means, ideally, observational data over a large field-of-view and spectroscopy at high spatial resolution. Methods. We present VIMOS integral field observations of 27 × 27 fields of view around four lensed quasars: HE 0230-2130, RX J0911.4 + 0551, H 1413 + 117 and B 1359 + 154. Using the low, medium and high resolution modes, we study the quasar images and the quasar environments. Because of the complexity of the reduction of integral field datasets, we provide a detailed report of the data reduction. Results. Comparison between the quasar spectra of the different images reveals differences for HE 0230-2130, RX J0911.4 + 0551 and H 1413+117: flux ratios between the images of the same quasar are different when measured in the emission lines and in the continuum. We have also measured the redshifts of galaxies in the neighborhood of HE 0230-2130 and RX J0911.4 + 0551 which possibly contribute to the total lensing potential, given their close proximity to the line-of-sight toward the quasars. Conclusions. A careful analysis reveals that microlensing is the most natural explanation for the (de)magnification of the continuum emitting region of the background sources. In HE 0230-2130, image D is likely to be affected by microlensing magnification; in RX J0911.4+0551, images A1 and A3 are likely to be modified by microlensing de-magnification and in H 1413+117 at least image D is affected by microlensing. We have not been able to recover any microlensing information or galaxies close to the line-of-sight in the neighborhood of B 1359+154.

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“…One could say that it is natural that the discovery of X-ray microlensing was made for this quasar, since the Einstein Cross QSO 2237+0305 is the most "popular" object to search for microlensing, because the first cosmological microlensing phenomenon was found by Irwin et al (1989) in this object and several groups have been monitoring the quasar QSO 2237+0305 to find evidence for microlensing. Microlensing has been suggested for the quasar MG J0414+0534 (Angonin-Willaime et al 1999) and for the quasar QSO H1413+117 (Remy et al 1996;Ostensen et al 1997;Turnshek et al 1997;Chae et al 2001). Therefore, in future may be a chance to find X-ray microlensing for other gravitationally lensed systems that have signatures of microlensing in the optical and radio bands.…”

Section: Discussionmentioning

confidence: 99%

On the contribution of microlensing to X-ray variability of high-redshifted QSOs

Popovic

Jovanović

2004

A&A

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Abstract. We consider a contribution of microlensing to the X-ray variability of high-redshifted QSOs. Such an effect could be caused by stellar mass objects (SMO) located in a bulge or/and in a halo of this quasar as well as at cosmological distances between an observer and a quasar. Here, we not consider microlensing caused by deflectors in our Galaxy since it is wellknown from recent MACHO, EROS and OGLE observations that the corresponding optical depth for the Galactic halo and the Galactic bulge is lower than 10 −6 . Cosmologically distributed gravitational microlenses could be localized in galaxies (or even in bulge or halo of gravitational macrolenses) or could be distributed in a uniform way. We have analyzed both cases of such distributions. As a result of our analysis, we obtained that the optical depth for microlensing caused by stellar mass objects is usually small for quasar bulge and quasar halo gravitational microlens distributions (τ ∼ 10 −4 ). On the other hand, the optical depth for gravitational microlensing caused by cosmologically distributed deflectors could be significant and could reach 10 −2 −0.1 at z ∼ 2. This means that cosmologically distributed deflectors may contribute significantlly to the X-ray variability of high-redshifted QSOs (z > 2). Considering that the upper limit of the optical depth (τ ∼ 0.1) corresponds to the case where dark matter forms cosmologically distributed deflectors, observations of the X-ray variations of unlensed QSOs can be used for the estimation of the dark matter fraction of microlenses.

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ESO & NOT photometric monitoring of the Cloverleaf quasar

Cited by 23 publications

References 7 publications

Polarization properties of broad absorption line QSOs: New statistical clues

Polarization properties of broad absorption line QSOs: New statistical clues

Integral field spectroscopy of four lensed quasars: analysis of their neighborhood and evidence for microlensing

On the contribution of microlensing to X-ray variability of high-redshifted QSOs

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