A Gravitationally lensed quasar discovered in OGLE

Zuzanna Kostrzewa-Rutkowska, Szymon Kozlowski, Cameron Lemon, T. Anguita, J. Greiner, M. W. Auger, L. Wyrzykowski, Y. Apostolovski, J. Bolmer, A. Udalski, M. K. Szymański, I. Soszyński, R. Poleski, P. Pietrukowicz, J. Skowron, P. Mróz, K. Ulaczyk, M. Pawlak

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11 Citations (Scopus)


We report the discovery of a new gravitationally lensed quasar (double) from the Optical Gravitational Lensing Experiment (OGLE) identified inside the ~670deg2 area encompassing the Magellanic Clouds. The source was selected as one of ~60 'red W1-W2' mid-infrared objects from WISE and having a significant amount of variability in OGLE for both two (or more) nearby sources. This is the first detection of a gravitational lens, where the discovery is made 'the other way around', meaning we first measured the time delay between the two lensed quasar images of -132 < tAB < -76 d (90 per cent CL), with the median tAB ~-102 d (in the observer frame), and where the fainter image B lags image A. The system consists of the two quasar images separated by 1.5 arcsec on the sky, with I ~20.0mag and I ~19.6mag, respectively, and a lensing galaxy that becomes detectable as I ~21.5 mag source, 1.0 arcsec from image A, after subtracting the two lensed images. Both quasar images show clear AGN broad emission lines at z=2.16 in the New Technology Telescope spectra. The spectral energy distribution (SED) fitting with the fixed source redshift provided the estimate of the lensing galaxy redshift of z ~0.9 ± 0.2 (90 per cent CL), while its type is more likely to be elliptical (the SED-inferred and lens-model stellar mass is more likely present in ellipticals) than spiral (preferred redshift by the lens model).

Original languageEnglish
Pages (from-to)663-672
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Publication statusPublished - 1 May 2018


  • Gravitational lensing: Strong
  • Methods: Observational
  • Quasars: General

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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