Testing General Relativity with Binary Lens Microlensing Events
Abstract
Einstein's General Relativity (GR), which has been precisely tested on galaxy and solar system scales, is still poorly constrained in extremely weak gravitational fields (with dimensionless Newtonian potentials of Φ∼ 10−8). In this Letter, we propose a new method to probe such a weak-field regime of gravity and measure the spatial curvature generated per unit mass. Specifically, binary microlensing events provide a laboratory to measure the parameterized post-Newtonian (PPN) parameter (γ), by combining the lensing mass (MlensGR) inferred from microlensing with the dynamical mass (Mdyn) determined from interferometric astrometry. Astrometric tracking of binary lenses was previously hindered by their faintness and minuscule angular separations (typically a few milliarcseconds). This limitation has been alleviated by the deployment of GRAVITY+, which pushes the instrument's sensitivity and astrometric precision to unprecedented heights. Based on astrometric simulations of the binary microlensing event ASASSN-22av, we directly estimate γ at the precision of ~23%. Such test of GR in the extremely weak-field regime can be further improved to much higher precision (~3%), based on more binary microlensing events with precise determination of the dynamical/lens mass.
Versions
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BibTeX
@misc{jin2026testing,
title = {{Testing General Relativity with Binary Lens Microlensing Events}},
author = {Xinyang Jin and Shuo Cao and Xuanni Chen and Yalong Nan and Xuchen Tai and Shuxun Tian},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.11949},
eprint = {2610.11949},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.11949},
}
RIS
TY - UNPB
TI - Testing General Relativity with Binary Lens Microlensing Events
AU - Xinyang Jin
AU - Shuo Cao
AU - Xuanni Chen
AU - Yalong Nan
AU - Xuchen Tai
AU - Shuxun Tian
PY - 2026
DA - 2026/10/08
PB - arXiv
DO - 10.48550/arxiv.2610.11949
UR - https://arxiv.org/abs/2610.11949
AB - Einstein's General Relativity (GR), which has been precisely tested on galaxy and solar system scales, is still poorly constrained in extremely weak gravitational fields (with dimensionless Newtonian potentials of Φ∼ 10^−8). In this Letter, we propose a new method to probe such a weak-field regime of gravity and measure the spatial curvature generated per unit mass. Specifically, binary microlensing events provide a laboratory to measure the parameterized post-Newtonian (PPN) parameter (γ), by combining the lensing mass (M_lens^GR) inferred from microlensing with the dynamical mass (M_dyn) determined from interferometric astrometry. Astrometric tracking of binary lenses was previously hindered by their faintness and minuscule angular separations (typically a few milliarcseconds). This limitation has been alleviated by the deployment of GRAVITY+, which pushes the instrument's sensitivity and astrometric precision to unprecedented heights. Based on astrometric simulations of the binary microlensing event ASASSN-22av, we directly estimate γ at the precision of ~23%. Such test of GR in the extremely weak-field regime can be further improved to much higher precision (~3%), based on more binary microlensing events with precise determination of the dynamical/lens mass.
ER -