- ID:
- ivo://CDS.VizieR/J/MNRAS/465/4914
- Title:
- R-band light curves of HE 0435-1223
- Short Name:
- J/MNRAS/465/4914
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from thirteen years of optically monitoring the gravitationally lensed z_QSO_= 1.693 quasar HE 0435-1223. The R-band light curves of the four individual images of the quasar were obtained using deconvolution photometry for a total of 876 epochs. Several sharp quasar variability features strongly constrain the time delays between the quasar images. Using two different numerical techniques, we measured these delays for all possible pairs of quasar images while always processing the four light curves simultaneously. For both methods, the delays are compatible with the previous measurements presented in Courbin et al. (2011, Cat. J/A+A/536/A53) that used a subset of the present data and a different curve-shifting method. Our analysis of random and systematic errors accounts in a realistic way for the observed quasar variability, fluctuating microlensing magnification over a broad range of temporal scales, noise properties, and seasonal gaps. Finally, we find that our time-delay measurement methods yield compatible results when applied to subsets of the data.
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- ID:
- ivo://CDS.VizieR/J/A+A/536/A53
- Title:
- R-band light curves of HE 0435-1223
- Short Name:
- J/A+A/536/A53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present accurate time delays for the quadruply imaged quasar HE 0435-1223. The delays were measured from 575 independent photometric points obtained in the R-band between January 2004 and March 2010. With seven years of data, we clearly show that quasar image A is affected by strong microlensing variations and that the time delays are best expressed relative to quasar image B.
- ID:
- ivo://CDS.VizieR/J/A+A/640/A105
- Title:
- R-band light curves of 23 lensed QSOs
- Short Name:
- J/A+A/640/A105
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of 15 years of monitoring lensed quasars, which was conducted by the COSMOGRAIL programme at the Leonhard Euler 1.2m Swiss Telescope. The decade-long light curves of 23 lensed systems are presented for the first time. We complement our data set with other monitoring data available in the literature to measure the time delays in 18 systems, among which nine reach a relative precision better than 15% for at least one time delay. To achieve this, we developed an automated version of the curve-shifting toolbox PyCS to ensure robust estimation of the time delay in the presence of microlensing, while accounting for the errors due to the imperfect representation of microlensing. We also re-analysed the previously published time delays of RXj1131-1231 and HE0435-1223, by adding six and two new seasons of monitoring, respectively, and confirming the previous time-delay measurements. When the time delay measurement is possible, we corrected the light curves of the lensed images from their time delay and present the difference curves to highlight the microlensing signal contained in the data. To date, this is the largest sample of decade-long lens monitoring data, which is useful to measure $H_0$ and the size of quasar accretion discs with microlensing as well as to study quasar variability.
- ID:
- ivo://CDS.VizieR/J/A+A/616/A183
- Title:
- R-band light curves of PG 1115+080
- Short Name:
- J/A+A/616/A183
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present time-delay estimates for the quadruply imaged quasar PG 1115+080. Our results are based on almost daily observations for seven months at the ESO MPIA 2.2m telescope at La Silla Observatory, reaching a signal-to-noise ratio of about 1000 per quasar image. In addition, we re-analyze existing light curves from the literature that we complete with an additional three seasons of monitoring with the Mercator telescope at La Palma Observatory. When exploring the possible source of bias we considered the so-called microlensing time delay, a potential source of systematic error so far never directly accounted for in previous time-delay publications. In fifteen years of data on PG 1115+080, we find no strong evidence of microlensing time delay. Therefore not accounting for this effect, our time-delay estimates on the individual data sets are in good agreement with each other and with the literature.
- ID:
- ivo://CDS.VizieR/J/A+A/556/A22
- Title:
- R-band light curves of RX J1131-1231
- Short Name:
- J/A+A/556/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results from nine years of optically monitoring the gravitationally lensed z_QSO_=0.658 quasar RX J1131-1231. The R-band light curves of the four individual images of the quasar were obtained using deconvolution photometry for a total of 707 epochs. Several sharp quasar variability features strongly constrain the time delays between the quasar images. Using three different numerical techniques, we measured these delays for all possible pairs of quasar images while always processing the four light curves simultaneously. For all three methods, the delays between the three close images A, B, and C are compatible with being 0, while we measured the delay of image D to be 91 days, with a fractional uncertainty of 1.5% (1{sigma}), including systematic errors. Our analysis of random and systematic errors accounts in a realistic way for the observed quasar variability, fluctuating microlensing magnification over a broad range of temporal scales, noise properties, and seasonal gaps. Finally, we find that our time-delay measurement methods yield compatible results when applied to subsets of the data.
- ID:
- ivo://CDS.VizieR/J/A+A/391/481
- Title:
- R-band photometry of SBS1520+530
- Short Name:
- J/A+A/391/481
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical R-band light curves of the gravitationally lensed quasar SBS 1520+530 derived from data obtained at the Nordic Optical Telescope, from February 1999 to May 2001. A time delay of 130+/-3days (1{sigma}) is determined from the light curves. In addition, spectra of SBS 1520+530 obtained at the Keck Observatory are spatially deconvolved in order to extract the spectrum of the faint lensing galaxy, free of any contamination by the light from the bright quasar images. This spectrum indicates a lens redshift z=0.717, in agreement with one of the absorption systems found in the quasar spectra. The best mass model of the system includes a second nearby galaxy and a cluster of galaxies in addition to the main lensing galaxy. Adopting this model and an {Omega}=0.3, {Lambda}=0.7 cosmology, our time-delay measurement yields a Hubble constant of H_0_=51+/-9km/s/Mpc (1{sigma} error).
- ID:
- ivo://CDS.VizieR/J/A+A/544/A51
- Title:
- R-band photometry of the lensed quasar UM673
- Short Name:
- J/A+A/544/A51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present observational data of the double lensed quasar UM673 obtained with the 1.5-m telescope of the Maidanak Observatory and the 1.3-m SMARTS telescope at CTIO between 2006 and 2010. We combine these data with our previously published observational data of UM673 to measure the time delay between the UM673 images. We also analyze the time evolution of the flux ratio between the UM673 images.
- ID:
- ivo://CDS.VizieR/J/A+A/642/A193
- Title:
- Rc-band light curves of 6 lensed QSOs
- Short Name:
- J/A+A/642/A193
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present six new time-delay measurements obtained from Rc-band monitoring data acquired at the MPIA 2.2m telescope at La Silla observatory between October 2016 and February 2020. The lensed quasars HE 0047-1756, WG 0214-2105, DES 0407-5006, 2M 1134-2103, PSJ 1606-2333 and DES 2325-5229 were observed almost daily at high signal-to-noise ratio to obtain high-quality light curves where we can record fast and small-amplitude variations of the quasars. We measure time delays between all pairs of multiple images with only one or two seasons of monitoring at the exception of the time delays relative to image D of PSJ 1606-2333. The most precise estimate is obtained for the delay between image A and image B of DES 0407-5006, with {tau}_AB_=-128.4^+3.5^_-3.8_ days (2.8% precision) including systematics due to extrinsic variability in the light curves. For HE 0047-1756, we combine our high-cadence data with measurements from decade-long light-curves from previous COSMOGRAIL campaigns, and reach a precision of 0.9 day on the final measurement. The present work demonstrates the feasibility of measuring time delays in lensed quasars in only one or two seasons, provided high signal-to-noise ratio data are obtained at a cadence close to daily.
- ID:
- ivo://CDS.VizieR/J/MNRAS/470/4838
- Title:
- Redshift catalog of HE 0435-1223 field-of-view
- Short Name:
- J/MNRAS/470/4838
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxies located in the environment or along the line of sight towards gravitational lenses can significantly affect lensing observables, and can lead to systematic errors on the measurement of H_0_ from the time-delay technique. We present the results of a systematic spectroscopic identification of the galaxies in the field of view of the lensed quasar HE 0435-1223 using the W.M. Keck, Gemini and ESO-Very Large telescopes. Our new catalogue triples the number of known galaxy redshifts in the direct vicinity of the lens, expanding to 102 the number of measured redshifts for galaxies separated by less than 3 arcmin from the lens. We complement our catalogue with literature data to gather redshifts up to 15 arcmin from the lens, and search for galaxy groups or clusters projected towards HE 0435-1223. We confirm that the lens is a member of a small group that includes at least 12 galaxies, and find 8 other group candidates near the line of sight of the lens. The flexion shift, namely the shift of lensed images produced by high-order perturbation of the lens potential, is calculated for each galaxy/group and used to identify which objects produce the largest perturbation of the lens potential. This analysis demonstrates that (i) at most three of the five brightest galaxies projected within 12 arcsec of the lens need to be explicitly used in the lens models, and (ii) the groups can be treated in the lens model as an external tidal field (shear) contribution.
- ID:
- ivo://CDS.VizieR/J/ApJ/888/35
- Title:
- Redshifts of lensed systems toward RXCJ2248.7-4431
- Short Name:
- J/ApJ/888/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an iterative method to construct a freeform lens model that self-consistently reproduces the sky positions, geometrically inferred redshifts, and relative brightnesses of all multiply lensed images toward a galaxy cluster. This method is applied to the cluster RXCJ2248.7-4431 (z=0.348) from the Hubble Frontier Fields program, toward which 10 multiply lensed sources with accurate spectroscopic redshifts and 6 others with inexact photometric redshifts have been identified. Using the spectroscopically secure systems to define an initial lens model, we compute the geometric redshifts of the photometric systems. We then iterate the lens model by incorporating the photometric systems at redshifts shifted by incremental amounts toward their geometric redshifts inferred from the previous step; on convergence, we find geometric redshifts in good agreement with the spectroscopically determined redshifts, but they can depart significantly from the photometrically determined redshifts. In the final lens model, all 16 lensed sources tightly follow the cosmological form of the angular diameter distance relation. Furthermore, although they are not used as model constraints, our lens model predicts relative brightnesses between image pairs for a given set of multiply lensed images in reasonable agreement with observations, thus providing independent validation of this model.
