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

A 5.5-year robotic optical monitoring of Q0957+561: substructure in a non-local cD galaxy

New light curves of the gravitationally lensed double quasar Q0957+561 in the gr bands during 2008-2010 include densely sampled, sharp intrinsic fluctuations with unprecedentedly high signal-to-noise ratio. These relatively violent flux variations allow us to very accurately measure the g-band and r-band time delays between the two quasar images A and B. Using correlation functions, we obtain that the two time delays are inconsistent with each other at the 2sigma level, with the r-band delay exceeding the 417-day delay in the g band by about 3 days. We also studied the long-term evolution of the delay-corrected flux ratio B/A from our homogeneous two-band monitoring with the Liverpool Robotic Telescope between 2005 and 2010. This ratio B/A slightly increases in periods of violent activity, which seems to be correlated with the flux level in these periods. The presence of the previously reported dense cloud within the cD lensing galaxy, along the line of sight to the A image, could account for the observed time delay and flux ratio anomalies.Comment: 8 pages, 6 figures, 4 tables, to appear in Astronomy and Astrophysic

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

New two-colour light curves of Q0957+561: time delays and the origin of intrinsic variations

We extend the gr-band time coverage of the gravitationally lensed double quasar Q0957+561. New gr light curves permit us to detect significant intrinsic fluctuations, to determine new time delays, and thus to gain perspective on the mechanism of intrinsic variability in Q0957+561. We use new optical frames of Q0957+561 in the g and r passbands from January 2005 to July 2007. These frames are part of an ongoing long-term monitoring with the Liverpool robotic telescope. We also introduce two photometric pipelines that are applied to the new gr frames of Q0957+561. The transformation pipeline incorporates zero-point, colour, and inhomogeneity corrections to the instrumental magnitudes, so final photometry to the 1-2% level is achieved for both quasar components. The two-colour final records are then used to measure time delays. The gr light curves of Q0957+561 show several prominent events and gradients, and some of them (in the g band) lead to a time delay between components of 417 +/- 2 d (1 sigma). We do not find evidence of extrinsic variability in the light curves of Q0957+561. We also explore the possibility of a delay between a large event in the g band and the corresponding event in the r band. The gr cross-correlation reveals a time lag of 4.0 +/- 2.0 d (1 sigma; the g-band event is leading) that confirms a previous claim of the existence of a delay between the g and r band in this lensed quasar. The time delays (between quasar components and between optical bands) from the new records and previous ones in similar bands indicate that most observed variations in Q0957+561 (amplitudes of about 100 mmag and timescales of about 100 d) are very probably due to reverberation within the gas disc around the supermassive black hole.Comment: 13 pages, 9 figures. Accepted for publication in A&