SDSS J1650+4251: A New Gravitational Lens

We report that the Sloan Digital Sky Survey quasar SDSS J165043.44+425149.3 is gravitationally lensed into two images, based on observations obtained with the WIYN 3.5 m telescope at the Kitt Peak National Observatory. The lensed quasar, at a redshift of z=1.547, appears as two images separated by 1.2" with B-band magnitudes of 17.8 and 20.0. The lensing galaxy is clearly detected in I-band images obtained in 0.3" seeing after point-spread function subtraction of the two quasar images. A strong metal-line absorption system is also identified in the unresolved SDSS spectrum of the double quasar, suggesting a plausible lens redshift of z=0.58. The UBRI flux ratios of the pair vary significantly, from 8.5:1 in the blue to 5.4:1 in the red, a difference of 0.5 mag, and are likely due to differential reddening through the lensing galaxy, microlensing in one or both quasar images, or some combination of the two. Optical monitoring of the quasar pair, particularly at blue wavelengths, will be needed to determine if microlensing is indeed significant. The predicted differential time delay between the quasar images is on the order of 1 month, assuming the intervening absorption system is due to the lensing galaxy.

Based on observations obtained with the WIYN telescope at the Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation. The WIYN Observatory is a joint facility of the University of Wisconsin-Madison, Indiana University, Yale University, and the National Optical Astronomy Observatory.