Adaptive PSF fitting – a highly performing photometric method and light curves of the GLS H1413+117: time delays and micro-lensing effects

Abstract

We present new photometric observations of H1413+117 acquired during seasons between 2001 and 2008 in order to estimate the time delays between the lensed quasar images and to characterize at best the on-going micro-lensing events. We propose a highly performing photometric method called the adaptive point spread function fitting and have successfully tested this method on a large number of simulated frames. This has enabled us to estimate the photometric error bars affecting our observational results. We analysed the V-and R-band light curves and V-R colour variations of the A-D components which show short-and long-term brightness variations correlated with colour variations. Using the χ 2 and dispersion methods, we estimated the time delays on the basis of the R-band light curves over the seasons between 2003 and 2006. We have derived the new values: t AB = −17.4 ± 2.1, t AC = −18.9 ± 2.8 and t AD = 28.8 ± 0.7 d using the χ 2 method (B and C are leading, D is trailing) with 1σ confidence intervals. We also used available observational constraints (resp. the lensed image positions, the flux ratios in mid-IR and two sets of time delays derived in the present work) to update the lens redshift estimation. We obtained z l = 1.95 +0.06 −0.10 which is in good agreement with previous estimations. We propose to characterize two kinds of micro-lensing events: micro-lensing for the A,

Gaia GraL: Gaia DR2 Gravitational Lens Systems. V. Doubly-imaged QSOs discovered from entropy and wavelets

“…If the time-resolved survey, in our case CRTS, had enough spatial resolution to derive two independent lightcurves, the detection of a possible multiply imaged quasar would be trivial. If the sampling is sufficient, a simple comparison of the lightcurves using some distance metric would reveal that they are likely the same lightcurve except for minor effects such as microlensing (e.g., Wambsganss & Paczynski 1991;Chae et al 2001;Akhunov et al 2017). Although microlensing can harm inferences of H 0 , it cannot prevent the identification of the two timeseries as realizations of the same underlying time-series, as expected from a gravitational lens.…”

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

“…A cross-correlation analysis of the RATCam light curves of the four images of QSO B1413+117 yielded three independent delays, which were also used to improve the lens solution for this system and to estimate the previously unknown lens redshift (Goicoechea & Shalyapin 2010). The mass model consisted of an SIE (main lensing galaxy), a singular isothermal sphere (secondary lensing galaxy), and external shear (MacLeod et al 2009), and we derived a lens redshift of z = 1.88 +0.09 −0.11 (1σ interval; see also Akhunov et al 2017). Additionally, from OSIRIS spectroscopy of field objects in the external shear direction, we identified an emission line galaxy at z ∼ 0.57 that is responsible for < 2% of γ ∼ 0.1 (Shalyapin & Goicoechea 2013).…”

Multiple MgII Absorption Systems in the Lines of Sight to Quadruply Lensed Quasar H1413+1143

“…The measurements of the time delays between the lensed images provide estimations of possible redshifts of the lensing galaxy, z lens ∼ 1.88−1.95 (e.g. Goicoechea & Shalyapin 2010;Akhunov et al 2017). Here we adopt the redshift of lens z lens = 1.90.…”

“…Kayser et al 1990;Goicoechea & Shalyapin 2010;Akhunov et al 2017). The measurements of the time delays with the Sloan Digital-Sky Survey improved the lens model for quasar H1413+1143 and provided estimations of possible redshifts of the lensing galaxy: z lens = 1.88 +0.09 −0.11 (Goicoechea & Shalyapin 2010) and 1.95 +0.06 −0.10 (Akhunov et al 2017). The time-delay measurements imply a possible redshift of the lensing galaxy: z lens ∼ 1.9.…”

“…For the lensed quasar H1413+1143, long-term photometric observations have been carried out to measure the time delays between the four lensed images (e.g. Kayser et al 1990;Goicoechea & Shalyapin 2010;Akhunov et al 2017). The measurements of the time delays with the Sloan Digital-Sky Survey improved the lens model for quasar H1413+1143 and provided estimations of possible redshifts of the lensing galaxy: z lens = 1.88 +0.09 −0.11 (Goicoechea & Shalyapin 2010) and 1.95 +0.06 −0.10 (Akhunov et al 2017).…”