EDP Sciences
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Volume 422, Number 2, August I 2004
Page(s) 477 - 482
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20040274

A&A 422, 477-482 (2004)
DOI: 10.1051/0004-6361:20040274

Anomalous fluctuations in observations of Q0957+561 A,B: Smoking gun of a cosmic string?

R. Schild1, I. S. Masnyak2, B. I. Hnatyk2 and V. I. Zhdanov2

1  Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
    e-mail: rschild@cfa.harvard.edu
2  Astronomical Observatory of Kyiv Taras Shevchenko National University, 3 Observatorna str., 04053 Kyiv, Ukraine

(Received 16 February 2004 / Accepted 25 March 2004)

We report the detection of anomalous brightness fluctuations in the multiple image Q0957 + 561 A,B gravitational lens system, and consider whether such anomalies have a plausible interpretation within the framework of cosmic string theory. We study a simple model of gravitational lensing by an asymmetric rotating string. An explicit form of the lens equation is obtained and approximate relations for magnification are derived. We show that such a model with typical parameters of the GUT string can quantitatively reproduce the observed pattern of brightness fluctuations. On the other hand explanation involving a binary star system as an alternative cause requires an unacceptably large massive object at a small distance. We also discuss possible observational manifestations of cosmic strings within our lens model.

Key words: cosmology: miscellaneous -- gravitational lensing -- galaxies: quasars: individual: Q0957+561 -- cosmology dark matter -- elementary particles

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© ESO 2004

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