SDSS J092455.87+021924.9: an Interesting Gravitationally Lensed Quasar from the Sloan Digital Sky Survey

Abstract

We report the discovery of a new gravitationally lensed quasar from the Sloan Digital Sky Survey, SDSS J092455.87+021924.9 (SDSS J0924+0219). This object was selected from among known SDSS quasars by an algorithm that was designed to select another known SDSS lensed quasar (SDSS 1226-0006A,B). Five separate components, three of which are unresolved, are identified in photometric follow-up observations obtained with the Magellan Consortium's 6.5m Walter Baade telescope at Las Campanas Observatory. Two of the unresolved components (designated A and B) are confirmed to be quasars with z=1.524; the velocity difference is less than 100 km sec^{-1} according to spectra taken with the W. M. Keck Observatory's Keck II telescope on Mauna Kea. A third stellar component, designated C, has the colors of a quasar with redshift similar to components A and B. The maximum separation of the point sources is 1.78". The other two sources, designated G and D, are resolved. Component G appears to be the best candidate for the lensing galaxy. Although component D is near the expected position of the fourth lensed component in a four image lens system, its properties are not consistent with being the image of a quasar at z~1.5. Nevertheless, the identical redshifts of components A and B and the presence of component C strongly suggest that this object is a gravitational lens. Our observations support the idea that a foreground object reddens the fourth lensed component and that another unmodeled effect (such as micro- or milli-lensing) demagnificates it, but we cannot rule out the possibility that SDSS0924+0219 is an example of the relatively rare class of ``three component'' lens systems.