From planes to spheres: About gravitational lens magnifications (2008)
We discuss the classic theorem according to which a gravitational lens always produces a total magnification greater than unity. This theorem seems to contradict the conservation of total flux from a...
Alba, A. Berciano, Garrett, M. A., Koopmans, L. V. E., Wucknitz, O.
Previous authors have reported the detection of intrinsically faint sub-mm emission lensed by the cluster MS0451.6-0305. They suggest that this emission arises from a merging system composed of a...
Metal Abundances in a Damped Lyman-alpha System Along Two Lines of Sight at z=0.93 (2005)
Lopez, S., Reimers, D., Gregg, M. D., Wisotzki, L., Wucknitz, O., Guzman, A.
We study metal abundances in the z=0.9313 damped Lya system observed in the two lines-of-sight, A and B, toward the gravitationally-lensed double QSO HE0512-3329. Spatially resolved STIS spectra...
A VLBI Study of the Gravitational Lens JVAS B0218+357 (2004)
Mittal, R., Porcas, R., Wucknitz, O., Biggs, A.
We present the results of phase-referenced VLBA+Effelsberg observations at five frequencies of the gravitational lens B0218+357 to establish the precise registration of the A and B lensed image...
York, T., Jackson, N., Browne, I. W. A., Wucknitz, O., Skelton, J. E.
We present deep optical observations of the gravitational lens system CLASS B0218+357, from which we derive an estimate of the Hubble constant. Extensive radio observations have reduced the...
We discuss the LensClean algorithm which for a given gravitational lens model fits a source brightness distribution to interferometric radio data in a similar way as standard Clean does in the...
Models for the lens and source of B0218+357 - A LensClean approach to determine H0 (2003)
Wucknitz, O., Biggs, A. D., Browne, I. W. A.
B0218+357 is one of the most promising systems to determine the Hubble constant from gravitational lenses. Consisting of two bright resolved images plus an Einstein ring, it provides better...
Disentangling microlensing and differential extinction in the double QSO HE0512-3329 (2003)
Wucknitz, O., Wisotzki, L., Lopez, S., Gregg, M. D.
We present the first separate spectra of both components of the small-separation double QSO HE0512-3329 obtained with HST/STIS in the optical and near UV. The similarities especially of the emission...
The HRX-BL Lac sample - evolution of BL Lac objects (2003)
Beckmann, V., Engels, D., Bade, N., Wucknitz, O.
The unification of X-ray and radio selected BL Lacs has been an outstanding problem in the blazar research in the past years. Recent investigations have shown that the gap between the two classes can...
Global 8.4-GHz VLBI observations of JVAS B0218+357 (2003)
Biggs, A. D., Wucknitz, O., Porcas, R. W., Browne, I. W. A., Jackson, N. J., Mao, S., ...
In this paper we present new observations of the gravitational lens system JVAS B0218+357 made with a global very long baseline interferometry (VLBI) network at a frequency of 8.4 GHz. Our maps have...
Global 8.4-GHz VLBI observations of JVAS B0218+357 (2002)
Biggs, A. D., Wucknitz, O., Porcas, R. W., Browne, I. W. A., Jackson, N. J., Mao, S., ...
In this paper we present new observations of the gravitational lens system JVAS B0218+357 made with a global VLBI network at a frequency of 8.4 GHz. Our maps have an rms noise of 30 microJy/beam and...
EVN/Global observations of the gravitational lens JVAS B0218+357 at 8.4 GHz (2002)
Biggs, A. D., Wucknitz, O., Porcas, R. W., Browne, I. W. A., Jackson, N. L., Mao, S., ...
High resolution optical and near-IR imaging of the quadruple quasar RX J0911.4+0551 (1998)
Burud, I., Courbin, F., Lidman, C., Jaunsen, A., Hjorth, J., Ostensen, R., ...
We report the detection of four images in the recently discovered lensed QSO RX J0911.4+0551. With a maximum angular separation of 3.1", it is the quadruply imaged QSO with the widest known angular...
High resolution optical and near-IR imaging of the quadruple quasar RX J0911.4+0551 (1970)
I. Burud, F. Courbin, C. Lidman, A. O. Jaunsen, J. Hjorth, M. I. Andersen, ...
We report the detection of four images in the recently discovered lensed QSO RX J0911.4+0551. With a maximum angular separation of 3:1 00 , it is the quadruply imaged QSO with the widest known...