Around‐the‐Clock Observations of the Q0957+561A,B Gravitationally Lensed Quasar. II. Results for the Second Observing Season

Colley, Wesley N.; Schild, Rudolph E.; Abajas, C.; Alcalde, D.; Aslan, Z.; Bikmaev, I.; Chavushyan, V.; Chinarro, Luis; Cournoyer, Jean-Philippe; Crowe, R.; Dudinov, V. N.; Evans, A.; Jeon, Young‐Beom; Goicoechea, L. J.; Golbasi, O.; Khamitov, I.; Kjernsmo, Kjetil; Lee, Hyun Ju; Lee, Jong‐Hwan; Lee, Ki Won; Lee, Myung Gyoon; López-Cruz, Omar; Mediavilla, E.; Moffat, A. F. J.; Mújica, R.; Ullán, A.; Muñoz, J. A.; Oscoz, A.; Park, Myeong‐Gu; Purves, N. G.; Saanum, Oyvind; Сахибуллин, Н. А.; Serra-Ricart, M.; Sinelnikov, I. Ye.; Stabell, R.; Stockton, Alan; Teuber, J.; Thompson, R. Stephen; Woo, Hwa-Sung; Zheleznyak, A. P.

doi:10.1086/368076

Cited by 33 publications

(25 citation statements)

References 20 publications

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“…The small decrease from one night to the next for both quasar images, in addition to the typically constant behaviour during each night, might be regarded as a tentative, short time‐scale manifestation of the much‐debated ‘zero lag correlation’ (between the theoretically unrelated A and B light curves) present in the brightness record of QSO 0957+561 (Kundic et al 1995; Colley et al 2003; Ovaldsen et al 2003). In the last reference, several conspicuous, simultaneous fluctuations were found in the quasar light curves, with time‐scales of up to several months and amplitudes up to 0.2 mag.…”

Section: Discussion and Summarymentioning

confidence: 91%

Five nights of intensiveR- andV-band photometry of QSO 0957+561A,B

Ovaldsen

Teuber

Stabell

et al. 2003

Monthly Notices of the Royal Astronomical Society

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We present R‐ and V‐band photometry of the gravitational lens system QSO 0957+561 from five nights (one in 2000 January and four in 2001 March, corresponding to the approximate time delay for the system) of uninterrupted monitoring at the Nordic Optical Telescope. In the photometry scheme we have stressed careful magnitude calibration as well as corrections for the lens galaxy contamination and the crosstalk between the twin (A and B) quasar images. The resulting, very densely sampled, light curves are quite stable, in conflict with earlier claims derived from the same data material. We estimate high‐precision timelag‐corrected B/A flux ratios in both colour bands, as well as V–R colour indices for A and B, and discuss the short time‐scale variability of the system.

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Section: Discussion and Summarymentioning

confidence: 91%

Five nights of intensiveR- andV-band photometry of QSO 0957+561A,B

Ovaldsen

Teuber

Stabell

et al. 2003

Monthly Notices of the Royal Astronomical Society

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“…2. Unfortunately, the EOCA monitoring campaign of QSO B0909+532 (Ullán et al 2006), QuOC-Around-The-Clock observations of QSO B0957+561 (Colley et al 2003) and the GLITP optical monitoring of QSO B2237+0305 could not be assembled in our disc-based storage for technical reasons.…”

Section: Sample Of Glqsmentioning

confidence: 99%

New database for a sample of optically bright lensed quasars in the northern hemisphere

Gil-Merino

Goicoechea

Shalyapin

et al. 2018

A&A

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In the framework of the Gravitational LENses and DArk MAtter (GLENDAMA) project, we present a database of nine gravitationally lensed quasars (GLQs) that have two or four images brighter than r = 20 mag and are located in the northern hemisphere. This new database consists of a rich variety of follow-up observations included in the GLENDAMA global archive, which is publicly available online and contains 6557 processed astronomical frames of the nine lens systems over the period 1999−2016. In addition to the GLQs, our archive also incorporates binary quasars, accretion-dominated radio-loud quasars, and other objects, where about 50% of the non-GLQs were observed as part of a campaign to identify GLQ candidates. Most observations of GLQs correspond to an ongoing long-term macro-programme with 2−10 m telescopes at the Roque de los Muchachos Observatory, and these data provide information on the distribution of dark matter at all scales. We outline some previous results from the database, and we additionally obtain new results for several GLQs that update the potential of the tool for astrophysical studies.

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“…So far, very few time delays are known with very high accuracy. Among the best examples are the double Q 0957+561 (Colley et al 2003), measured in optical wavelengths, and the quadruple B 1608+656 (Fassnacht et al 2002), measured in radio wavelengths. Most other lensed quasars have time delays known with a precision of about 10%.…”

Section: Which Accuracy?mentioning

confidence: 99%

COSMOGRAIL: The COSmological MOnitoring of GRAvItational Lenses

Eigenbrod¹,

Courbin²,

Vuissoz³

et al. 2005

A&A

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Abstract. We use numerical simulations to test a broad range of plausible observational strategies designed to measure the time delay between the images of gravitationally lensed quasars. Artificial quasar light curves are created along with Monte-Carlo simulations in order to determine the best temporal sampling to adopt when monitoring the photometric variations of systems with time delays between 5 and 120 days, i.e., always shorter than the visibility window across the year. Few and realistic assumptions are necessary on the quasar photometric variations (peak-to-peak amplitude and time-scale of the variations) and on the accuracy of the individual photometric points. The output of the simulations is the (statistical) relative error made on the time delay measurement, as a function of 1-the object visibility over the year; 2-the temporal sampling of the light curves; and 3-the time delay. Also investigated is the effect of long term microlensing variations which must be below the 5% level (either intrinsically or by subtraction) if the goal is to measure time delays with an accuracy of 1-2%. However, while microlensing increases the random error on the time delay, it does not significantly increase the systematic error, which is always a factor 5 to 10 smaller than the random error. Finally, it is shown that, when the time delay is comparable to the visibility window of the object, a logarithmic sampling can significantly improve the time delay determination. All results are presented in the form of compact plots to be used to optimize the observational strategy of future monitoring programs.Key words. gravitational lensing -cosmological parameters -cosmology: observations Measuring time delaysMeasuring time delays in gravitationally lensed quasars is difficult, but not as difficult as it first appeared in the late eighties when the first monitoring programs were started. Obtaining regular observing time on telescopes in good sites was (and is still) not easy and the small angular separations between the quasar images require to perform accurate photometry of blended objects, sometimes with several quasar images plus the lensing galaxy within the seeing disk. COSMOGRAILThe COSMOGRAIL project (COSmological MOnitoring of GRAvItational Lenses), started in April 2004, addresses both issues of carrying out photometry of faint blended sources and of obtaining well sampled light curves of lensed quasars.The project involves 5 telescopes: (1) the Swiss 1.2 m Euler telescope located at La Silla, Chile; (2) the Swiss-Belgian 1.2 m Mercator telescope, located in the Canaria islands (La Palma, Spain); (3) the 2 m robotic telescope of the Liverpool University (UK), also located at La Palma; (4) the 1.5 m telescope of Maidanak observatory in Uzbekistan; and (5) the 2 m Himalayan Chandra Telescope (HCT).All 5 telescopes, and others that will join the collaboration, are used in order to follow the photometric variations of most known gravitationally lensed quasars that are suitable for a determination of H 0 . The sample of...

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Around‐the‐Clock Observations of the Q0957+561A,B Gravitationally Lensed Quasar. II. Results for the Second Observing Season

Cited by 33 publications

References 20 publications

Five nights of intensiveR- andV-band photometry of QSO 0957+561A,B

Five nights of intensiveR- andV-band photometry of QSO 0957+561A,B

New database for a sample of optically bright lensed quasars in the northern hemisphere

COSMOGRAIL: The COSmological MOnitoring of GRAvItational Lenses

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