Newly discovered quadruply lensed quasar

Hi all,

ArXiv today has an article about 22 newly discovered lensed quasars found in the Gaia DR2 data. The quasars were found by checking for multiple Gaia detections around objects in quasar candidate catalogues, modelling of unWISE coadd pixels using Gaia astrometry, and Gaia detections offset from photometric and spectroscopic galaxies. Follow up spectra were obtained for 33 candidates leaving 22.

Most of these have Gaia G magnitudes of 19 and fainter, making them impossible to observe visually, though some of them are somewhat brighter and one of them (J2145+6345) may be in reach our telescopes. The Gaia G magnitudes of the four components are 16.86, 17.26, 18.34 and 18.56 (Table 4, page 9), the Pan-STARRS g magnitudes are 17.79, 17.70, 18.28 and 19.14 (Appendix A, page 18) and the Pan-STARRS r magnitudes are 17.28, 17.04, 18.32 and 18.55 (Appendix A, page 18) respectively.

Good luck hunting this one (and possibly others) down!


Clear skies, Wouter

What's the cut-off Gaia G magnitude after which lensed quasars can be visually observed btw?

It depends on the type of object but in case of quasars, which have a flat spectrum in optical wavelengths, this formula holds pretty well:

V = G + 0.5