A&A 422, 477-482 (2004)
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
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
© ESO 2004