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Extrinsic Radio Variability of JVAS/CLASS Gravitational Lenses

Koopmans, L. V. E. and Biggs, A. and Blandford, R. D. and Browne, I. W. A. and Jackson, N. J. and Mao, S. and Wilkinson, P. N. and de Bruyn, A. G. and Wambsganss, J. (2003) Extrinsic Radio Variability of JVAS/CLASS Gravitational Lenses. Astrophysical Journal, 595 (2). pp. 712-718. ISSN 0004-637X. doi:10.1086/377434.

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We present flux ratio curves of the fold and cusp (i.e., close multiple) images of six Jodrell Bank VLA Astrometric Survey and Cosmic Lens All-Sky Survey (JVAS/CLASS) gravitational lens systems. The data were obtained over a period of 8.5 months in 2001 with the Multi Element Radio-Linked Interferometer Network (MERLIN) at 5 GHz with 50 mas resolution, as part of a MERLIN Key Project. Even though the time delays between the fold and cusp images are small (≾1 day) compared to the timescale of intrinsic source variability, all six lens systems show evidence that suggests the presence of extrinsic variability. In particular, the cusp images of B2045+265—regarded as the strongest case of the violation of the cusp relation (i.e., the sum of the magnifications of the three cusp images add to zero)—show extrinsic variations in their flux ratios up to ~40% peak to peak on timescales of several months. Its low Galactic latitude of b ≈ -10° and a line of sight toward the Cygnus superbubble region suggest that Galactic scintillation is the most likely cause. The cusp images of B1422+231 at b ≈ +69° do not show strong extrinsic variability. Galactic scintillation can therefore cause significant scatter in the cusp and fold relations of some radio lens systems (up to 10% rms), even though these relations remain violated when averaged over a ≾1 yr time baseline.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Koopmans, L. V. E.0000-0003-1840-0312
Biggs, A.0000-0002-1117-9961
Blandford, R. D.0000-0002-1854-5506
Mao, S.0000-0001-8317-2788
Additional Information:© 2003 The American Astronomical Society. Received 2003 March 13; accepted 2003 June 9. L. V. E. K. acknowledges the support from an STScI Fellowship grant. R. D. B. is supported by an NSF grant AST-0206286. MERLIN is a National Facility operated by the University of Manchester at Jodrell Bank Observatory on behalf of PPARC. L. V. E. K. thanks Chris Kochanek and Neal Dalal for suggestions that improved the presentation of this work. We thank the referee for helping to clarify the manuscript.
Funding AgencyGrant Number
Space Telescope Science InstituteUNSPECIFIED
Subject Keywords:gravitational lensing — ISM: general — scattering
Issue or Number:2
Record Number:CaltechAUTHORS:20190604-082923178
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Official Citation:L. V. E. Koopmans et al 2003 ApJ 595 712
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:96100
Deposited By: Tony Diaz
Deposited On:04 Jun 2019 18:24
Last Modified:16 Nov 2021 17:18

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