Verification of Einstein’s formula for gravitational deflection of light using observations of galactic microlensing

1Alexandrov, AN, 1Zhdanov, VI, Slusar, VM
1Astronomical Observatory of Taras Shevchenko National University of Kyiv, Kyiv, Ukraine
Kinemat. fiz. nebesnyh tel (Online) 2020, 36(5):3-14
Start Page: Extragalactic Astronomy
Language: Ukrainian

General relativity (GR) has a solid experimental base. However, the emergence of new experimental capabilities and independent observational information stimulates the continuation of tests of general relativity. The purpose of this work is to evaluate the potential of gravitational microlensing of distant sources on the stars of our Galaxy and to verify the Einstein formula of the gravitational refraction. This effect has been repeatedly tested in the Solar System in the high-accuracy experiments with the propagation of radio waves, when the measurements are most effective for the distances from the signal trajectory to the Sun of the order of several solar radii. In the case of galactic microlensing, a quite different type of observational data and other characteristic distances are used that in the high magnification events are determined by the Einstein ring radii, which is typically of the order of 1 au. It should be noted that, although the gravitational deflections of light by stars are very small and currently practically inaccessible by direct measurements, however, due to the large distances to the microlenses, the radiation flux from the source in strong microlensing events of can increase several times. To verify Einstein’s formula, we consider a more general dependence of the beam deflection angle on its impact distance p relative to the deflector: and, accordingly, modify the equations of gravitational lensing. The challenge is to limit based on observational data. We use the Early Warning System data obtained in 2018 within Optical Gravitational Lensing Experiment (OGLE) ( ogle4/ews/2019/ews.html). We formed a sample of 100 light curves from the data obtained by the OGLE group in 2018. Each light curve was fitted as part of a modified model of gravitational lensing with parameter ε. As a result, 100 values of ε and estimates of their variances were obtained. We found that the mean value of ε does not contradict GR within the limits of a one percent standard deviation. In the future, using a larger number of light curves allows us to hope for a significant decrease in the error of due to statistical averaging.

Keywords: General Relativity tests, gravitational light deflection, gravitational microlensing, light curves

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