MiNDSTEp differential photometry of the gravitationally lensed quasars WFI 2033-4723 and HE 0047-1756: microlensing and a new time delay

Abstract

Aims. We present V and R photometry of the gravitationally lensed quasars WFI 2033-4723 and HE 0047-1756. The data were taken by the MiNDSTEp collaboration with the 1.54 m Danish telescope at the ESO La Silla observatory from 2008 to 2012. Methods. Differential photometry has been carried out using the image subtraction method as implemented in the HOTPAnTS package, additionally using GALFIT for quasar photometry. Results. The quasar WFI 2033-4723 showed brightness variations of order 0.5 mag in V and R during the campaign. The two lensed components of quasar HE 0047-1756 varied by 0.2-0.3 mag within five years. We provide, for the first time, an estimate of the time delay of component B with respect to A of ∆t = (7.6 ± 1.8) days for this object. We also find evidence for a secular evolution of the magnitude difference between components A and B in both filters, which we explain as due to a long-duration microlensing event. Finally we find that both quasars WFI 2033-4723 and HE 0047-1756 become bluer when brighter, which is consistent with previous studies.

The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2017/2018 follow-up campaign: discovery of 10 lensed quasars and 10 quasar pairs

“…This problem has been well-explored by teams dedicated to lensed quasar monitoring for extraction of lightcurves and hence time delays. In particular, photometry has been extracted through fitting multiple PSFs (e.g., Goicoechea & Shalyapin 2010;Koptelova et al 2010), fitting multiple PSFs and parametric galaxy components (e.g., Kochanek et al 2006b;Shalyapin & Goicoechea 2017;Hainline et al 2013), difference imaging (e.g., Fohlmeister et al 2013;Giannini et al 2017), aperture photometry for wideseparation systems (e.g., Ovaldsen et al 2003;Dahle et al 2015), and non-parametric deconvolutional techniques (e.g., Burud et al 2002;Vuissoz et al 2007;Bonvin et al 2018).…”

Gravitational grating

“…In the strong-lensing systems with the multiple images from a quasar, by time shifting the light curves of images with the amount of time delay, we can remove the intrinsic variations of a quasar to extract our desired foreground signals. This method has been used for detection of the microlensing signals (Giannini et al 2017) as well as the weaklensing effect by the dark micro-halos (Rahvar et al 2014) in the quasars light curve. Since the time-scale of microlensing and dark micro-halo transits are longer than the transit time-scale of diffraction fringes from the GW, in principle we can filter out these two backgrounds.…”

Cosmological Distance Indicators

“…Other recent studies for specific objects include Giannini et al [2017] for WFI 2033−4723 and HE 0047−1756, and Shalyapin and Goicoechea [2017] reporting a delay for SDSS J1515+1511. Hainline et al [2013] measure a tentative time delay for SBS 0909+532, although the curves suffer from strong microlensing.…”

“…Early results from the OSU program were obtained in 2006 for HE 0435−1223 [Kochanek et al, 2006] while COSMO-GRAIL delivered its first results starting in 2007 for SDSS J1650+4251 [Vuissoz et al, 2007], WFI J2033−4723 [Vuissoz et al, 2008] and HE 0435−1223 [Courbin et al, 2011a]. More recent time-delay measurements from COSMOGRAIL were obtained for RX J1131−1231 [Tewes et al, 2013b], HE 0435−1223 [Bonvin et al, 2017] as well as SDSS J1206+4332 and HS 2209+1914 [Eulaers et al, 2013] Other recent studies for specific objects include Giannini et al [2017] for WFI 2033−4723 and HE 0047−1756, and Shalyapin and Goicoechea [2017 reporting a delay for SDSS J1515+1511. Hainline et al [2013] measure a tentative time delay for SBS 0909+532, although the curves suffer from strong microlensing.…”