Time-Domain Studies of Gravitationally Lensed Quasars

Abstract

Abstract. We present an overview and current results of an ongoing optical/NIR monitoring of seven gravitationally-lensed quasars (GLQs) with the 2-m Liverpool Robotic Telescope. The photometric data from the first seven years (2005)(2006)(2007)(2008)(2009)(2010)(2011) of this programme 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 signals in certain GLQs. Thus, some GLQs in our sample allow us to assess their extrinsic and intrinsic variations; we then discuss the origin of both kinds of fluctuations. We also demonstrate the usefulness of GLQ time-domain data for obtaining successful reverberation maps of the inner regions of accretion disks around distant supermassive black holes, and for estimating the redshifts of distant lensing galaxies.Keywords. gravitational lensing, black hole physics, accretion, galaxies: general, quasars: general.An overview of our ongoing Liverpool Quasar Lens Monitoring (LQLM) project is presented in Table 1. The data collection are being carried out in different phases: LQLM I (from 2005 January to 2007 July), LQLM II (from 2008 February to 2010 July) and LQLM III (from 2010 October to the present), and is using available optical/NIR instrumentation. The relevant instruments on the Liverpool Robotic Telescope are the RATCam CCD camera and its associated Sloan griz filter set, the RINGO2 optical polarimeter, and the FRODOspec spectrograph (3900-9400Å). Some astrophysical results and expectations for each target GLQ are given here; a more complete and updated information can be found on the GLENDAMA website http://grupos.unican.es/glendama. SBS 0909+532. The LQLM I light curves in the r band led to a robust time-delay between its two images of ∆t AB = −49 ± 6 days and ∆t ij = t j −t i , B leading (Goicoechea et al. 2008a). In addition, the optical flux ratio A/B changed little in the first 10 years of observations, i.e., between the identification as a quasar pair in 1996 and our LQLM I campaign (see Dai & Kochanek 2009 and references therein). For example, the r-band light curve of the A image and the properly shifted r-band light curve of B were consistent with each other throughout the LQLM I period, so the variability over this time segment was basically intrinsic to the distant quasar (Goicoechea et al. 2008a). However, the LQLM III light curves indicate that the r-band flux ratio had evolved in 2010-2011. Gravitational microlensing by stars within the main lensing galaxy could account for the detected extrinsic variation.FBQ 0951+2635. Gravitational microlensing seems to be an important variability mechanism for this GLQ (Paraficz et al. 2006;Shalyapin et al. 2009). We are taking a few frames per year in the r band to trace the long-term behaviour of A/B, and thus to † On behalf of the GLENDAMA Project Team.

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

“…Immediately after the discovery of the double quasar SDSS J1339+1310 (Inada et al 2009), we began a robotic monitoring programme with the LT in the SDSS r passband (Goicoechea & Shalyapin 2012). Our photometric observations were performed in 2009 and 2012−2015, and from 13 January to 8 February 2016, so they span five seasons of ∼ 4−6 months each (tipically from January or February to July) and the beginning of the current season.…”

Deep optical imaging and spectroscopy of the lens system SDSS J1339+1310

“…In Fig. 4, the circles and the square show fluxes from our photometric monitoring programme with the 2.0 m Liverpool Telescope (LT) in the r band (Goicoechea & Shalyapin 2012) and the NOT stacked frame in the left panel of Fig. 1.…”

“…A main goal of our Liverpool quasar lens monitoring (LQLM) project is to build a rich time-domain database for several lens systems (Goicoechea & Shalyapin 2012). This robotic optical monitoring is complemented with other relevant observations, such as deep optical imaging and spectroscopy of the quasar fields (e.g., Shalyapin & Goicoechea 2013).…”