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J. A. Blackburne, P. L. Schechter (MIT), L. Wisotzki (Universitat Potsdam)
The Hamburg-ESO quasar HE 1113-0641 is found to be a quadruple gravitational lens, based on observations in two epochs with the twin 6.5m Magellan telescopes at Las Campanas Observatory. The quasar is at a redshift of 1.235, and its four components appear in a cross configuration, with i'-band magnitudes ranging from 18.0 to 18.8. With a maximum image separation of 0.65 arcsec, this is the smallest-separation quadruple ever identified using a ground-based optical telescope. PSF subtraction reveals the lensing galaxy, particularly in subsequent observations using the Hubble Space Telescope. The components' flux ratios vary a small amount between filters and epochs (e.g. from 1.7:1 to 1.4:1 for the C component), and do not at all agree with lens model predictions. Their HST F555W-F814W and F814W-F160W colors display an rms variation of 0.14 magnitudes. We estimate the redshift probability distribution of the lensing galaxy, arriving at a median lens redshift of 0.75. With this redshift, the maximum time delay of the lens of 1.7 days, suggesting that the flux ratios and color variation are not due to variability of the quasar, but may result from differential extinction in the lensing galaxy or from microlensing. The authors gratefully acknowledge support from the US NSF under award AST0206010 and from NASA under award HST-GO-09744-07-A.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.