KRONE-MARTINS, A.; GRAHAM, M. J.; STERN, D.; DJORGOVSKI, S. G.; DELCHAMBRE, L.; DUCOURANT, C.; TEIXEIRA, R.; DRAKE, A. J.; SCARANO JR., S.; SURDEJ, J.; GALLUCCIO, Laurent; JALAN, P.; WERTZ, O.; KLÜTER, J.; MIGNARD, F.; SPINDOLA-DUARTE, C.; DOBIE, D.; SLEZAK, E.; SLUSE, D.; MURPHY, T.; BOEHM, C.; NIERENBERG, A. M.; BASTIAN, U.; WAMBSGANSS, J.; LECAMPION, J. -F.

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The discovery of multiply-imaged gravitationally lensed QSOs is fundamental to many astronomical and cosmological studies. However, these objects are rare and challenging to discover due to requirements of high-angular resolution astrometric, multiwavelength photometric and spectroscopic data. This has limited the number of known systems to a few hundred objects. We aim to reduce the constraints on angular resolution and discover multiply-imaged QSO candidates by using new candidate selection principles based on unresolved photometric time-series and ground-based images from public surveys. We selected candidates for multiply-imaged QSOs based on low levels of entropy computed from Catalina unresolved photometric time-series or Euclidean similarity to known lenses in a space defined by the wavelet power spectra of Pan-STARSS DR2 or DECaLS DR7 images, combined with multiple {\it Gaia} DR2 sources or large astrometric errors and supervised and unsupervised learning methods. We then confirmed spectroscopically some candidates with the Palomar Hale, Keck-I, and ESO/NTT telescopes. Here we report the discovery and confirmation of seven doubly-imaged QSOs and one likely double quasar. This demonstrates the potential of combining space-astrometry, even if unresolved, with low spatial-resolution photometric time-series and/or low-spatial resolution multi-band imaging to discover multiply-imaged lensed QSOs.< Réduire

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Laboratoire d'Astrophysique de Bordeaux (LAB) - UMR 5804