EDP Sciences
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Volume 373, Number 3, July III 2001
Page(s) L25 - L28
Section Letters
DOI http://dx.doi.org/10.1051/0004-6361:20010748

A&A 373, L25-L28 (2001)
DOI: 10.1051/0004-6361:20010748

Sub-milliarcsec-scale structure of the gravitational lens B1600+434

A. R. Patnaik1 and A. J. Kemball2

1  Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
    e-mail: apatnaik@mpifr-bonn.mpg.de
2  National Radio Astronomy Observatory, PO Box 0, Socorro, NM 87801, USA

(Received 6 March 2001 / Accepted 25 May 2001 )

In the gravitational lens system B1600+434 the brighter image, A, is known to show rapid variability which is not detected in the weaker image, B (Koopmans & de Bruyn 2000). Since correlated variability is one of the fundamental properties of gravitational lensing, it has been proposed that image A is microlensed by stars in the halo of the lensing galaxy (Koopmans & de Bruyn 2000). We present VLBA observations of B1600+434 at 15 GHz with a resolution of 0.5 milliarcsec to determine the source structure at high spatial resolution. The surface brightness of the images are significantly different, with image A being more compact. This is in apparent contradiction with the required property of gravitational lensing that surface brightness be preserved. Our results suggest that both the lensed images may show two-sided elongation at this resolution, a morphology which does not necessarily favour superluminal motion. Instead these data may suggest that image B is scatter-broadened at the lens so that its size is larger than that of A, and hence scintillates less than image A.

Key words: gravitational lensing -- (galaxies:) quasars: individual: B1600+434 -- radio continuum: galaxies

Offprint request: A. J. Kemball, akemball@nrao.edu

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