Journal Article

Observations of time delays in gravitational lenses from intensity fluctuations: the coherence function

Ermanno F. Borra

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 389, issue 1, pages 364-370
Published in print September 2008 | ISSN: 0035-8711
Published online August 2008 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13568.x
Observations of time delays in gravitational lenses from intensity fluctuations: the coherence function

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Measurements of the spectrum of the fluctuations of the output current of the quadratic detector of a telescope can be used to find unresolved astronomical gravitational lenses and determine time delays between their image components. These time delays can be used for astronomical studies. The spatial correlation coefficient of a source is an important parameter that quantifies the loss of contrast, caused by the extendedness of the source, in the spectral modulation of the intensity fluctuations. This work shows that the correlation coefficient must not be evaluated at the frequency of observation, but must instead be evaluated at the much lower beat frequencies of the spectrum of the fluctuations. This opens up a powerful, novel technique to find unresolved gravitational lenses and to study the lensing event and the source.

Keywords: gravitational lensing; methods: observational; techniques: interferometric

Journal Article.  6281 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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