Gravitational lens system SDSS J1339+1310: microlensing factory and time delay

We spectroscopically re-observed the gravitational lens system SDSS J1339+1310 using OSIRIS on the GTC. We also monitored the $r$-band variability of the two quasar images (A and B) with the LT over 143 epochs in the period 2009$-$2016. These new data in both the wavelength and time domains have confirmed that the system is an unusual microlensing factory. The C$\scriptsize{\rm{IV}}$ emission line is remarkably microlensed, since the microlensing magnification of B relative to that for A, $\mu_{\rm{BA}}$, reaches a value of 1.4 ($\sim$ 0.4 mag) for its core. Moreover, the B image shows a red wing enhancement of C$\scriptsize{\rm{IV}}$ flux (relative to A), and $\mu_{\rm{BA}}$ = 2 (0.75 mag) for the C$\scriptsize{\rm{IV}}$ broad-line emission. Regarding the nuclear continuum, we find a chromatic behaviour of $\mu_{\rm{BA}}$, which roughly varies from $\sim$ 5 (1.75 mag) at 7000 \AA\ to $\sim$ 6 (1.95 mag) at 4000 \AA. We also detect significant microlensing variability in the $r$ band, and this includes a number of microlensing events on timescales of 50$-$100 d. Fortunately, the presence of an intrinsic 0.7 mag dip in the light curves of A and B, permitted us to measure the time delay between both quasar images. This delay is $\Delta t_{\rm{AB}}$ = 47$^{+5}_{-6}$ d (1$\sigma$ confidence interval; A is leading), in good agreement with predictions of lens models.Comment: Accepted to A&A; 19 pages, 2 appendices, 3 long tables (Tables 1-3). Tables 1-2 and an updated version of Table 3 are available at http://grupos.unican.es/glendama/q1339.ht

Time-domain studies of gravitationally lensed quasars (GLQs)

We present the overview and current results of an ongoing optical/NIR monitoring of seven GLQs with the 2-m Liverpool Robotic Telescope. The photometric data over the first seven years of this programme (2005-2011) are leading to high-quality light curves, which in turn are being used as key tools for different standard and novel studies. While brightness records of non-lensed distant quasars may contain unrecognized extrinsic variations, one can disentangle intrinsic from extrinsic signal in certain GLQs. Thus, some GLQs in our sample allow us to assess their extrinsic and intrinsic variations, as well as to discuss the origin of both kinds of fluctuations. We also demonstrate the usefulness of GLQ time-domain data to obtain successful reverberation maps of inner regions of accretion disks around distant supermassive black holes, and to estimate redshifts of distant lensing galaxies.Comment: 3 pages, 1 figure, 1 table, New Horizons in Time Domain Astronomy, Proceedings IAU Symposium 285, R.E.M. Griffin, R.J. Hanisch and R. Seaman, eds. (2012

Time delays in the gravitationally lensed quasar H1413+117 (Cloverleaf)

The quadruple quasar H1413+117 (zs = 2.56) has been monitored with the 2.0 m Liverpool Telescope in the r Sloan band from 2008 February to July. This optical follow-up leads to accurate light curves of the four quasar images (A–D), which are defined by 33 epochs of observation and an average photometric error of ∼15 mmag. We then use the observed (intrinsic) variations of ∼50–100 mmag to measure the three time delays for the lens system for the first time (1σ confidence intervals): ΔτAB = −17 ±  3, ΔτAC = −20 ±  4, and ΔτAD = 23 ±  4 days (Δτij = τj − τi; B and C are leading, while D is trailing). Although time delays for lens systems are often used to obtain the Hubble constant (H0), the unavailability of the spectroscopic lens redshift (zl) in the system H1413+117 prevents a determination of H0 from the measured delays. In this paper, the new time-delay constraints and a concordance expansion rate (H0 = 70 km s−1 Mpc−1) allow us to improve the lens model and to estimate the previously unknown zl. Our 1σ estimate zl = 1.88+0.09−0.11 is an example of how to infer the redshift of very distant galaxies via gravitational lensing.The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. We thank the Liverpool Telescope staff for kind interaction over the observation period (program ID: CL08A03). We use data sets taken from the Sloan Digital Sky Survey (SDSS) Web site, and we are grateful to the SDSS team for doing that public database. This research has been supported by the Spanish Department of Education and Science grant AYA2007-67342-C03-02, and University of Cantabria funds

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

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.Comment: Accepted to A&A; 32 pages. Tables 4-6, 8-11 and 13-16 are only available in electronic form at the CDS and https://grupos.unican.es/glendama/LQLM_results.ht

Robotic monitoring of gravitationally lensed quasars

We report on the first observational phase of the Liverpool Quasar Lens Monitoring (LQLM) project. This mainly consisted of the optical follow-up of three lensed quasars using the 2 m Liverpool Robotic Telescope. The observational subprogram started in January 2005 and was completed in July 2007. We also describe our photometric approaches (including two pipelines to extract accurate and reliable fluxes of images of lensed quasars), the performance of the telescope when taking modest nightly exposures of lens systems, and the main scientific results from the observed light curves. The LQLM archive and the current status of the project (second phase) are also outlined.The authors are grateful to the organizers (LOC and SOC) of the workshop on Robotic Autonomous Observatories held in Malaga from 18 to 21 May 2009, who prepared a useful meeting showing current robotic facilities as well as the efforts of several groups in different fields and some ongoing projects. They thank several members of the Liverpool Telescope staff (M. Bode, C. Moss, R. Smith, and I. Steele) for guidance in the preparation of their robotic monitoring project and kind interaction during the last five years. The Liverpool Telescope is operated on the island of La Palma by Liverpool John Moores University in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council. They thank R. Gil-Merino and B. McLeod for different kinds of support during the first stages of the LQLM project. Their LQLM project is being developed in parallel with a similar project at the Maidanak Observatory. They also thank T. Akhunov, B. Artamonov, O. Burkhonov, E. Koptelova, S. Nuritdinov, A. Sergeyev, and A. Zheleznyak for collaboration, discussion and exchange of information on common targets. They use information taken from the Sloan Digital Sky Survey (SDSS) Web site, and they are grateful to the SDSS team for doing that public database. This research has been financially supported by the Spanish Department of Education and Science Grants AYA2004-08243-C03-02 and AYA2007-67342-C03-02, and University of Cantabria funds