The Response of the Tests of General Relativity on Black Hole Mimicker Binaries using Gravitational-Wave Observations

The majority of the standard tests of the general theory of relativity (GR) performed with the LIGO-Virgo-KAGRA collaboration follow the assumption that the sources are binaries of black holes or neutron stars. However, a broad class of alternative compact objects—often termed black hole mimickers, such as boson stars and gravastars—can produce gravitational wave signals nearly indistinguishable from those of binary black holes. These systems may arise from GR minimally coupled to non-Standard Model fields, such as ultralight scalars, or from theories with non-minimal couplings in which the scalar field effectively becomes part of the gravitational sector. In this work, we have performed parameterized tests of GR—including the TIGER, FTI, and propagation test MDR frameworks, as well as the pSEOBNR ringdown test—on publicly available numerical-relativity waveforms of equal-mass, quasi-circular boson-star binaries with varying compactness. We further applied the spin-induced multipole-moment test to probe deviations from the black-hole nature of these systems. All analyses are conducted assuming the fifth observing run sensitivity of the LIGO–Virgo network at a fixed luminosity distance of 400 Mpc. We will present the results from these tests and discuss which of these tests could lead to an apparent GR violation.