We study how a solitonic core of ultralight bosonic dark matter (ULBDM) around a Schwarzschild black hole influences the spacetime geometry and the resulting high-frequency quasi-periodic oscillations (HF QPOs) observed in X-ray binaries. The analysis is based on four well-known sources: GRS 1915+105, XTE J1859+226, XTE J1550-564, and GRO J1655-40, with observed twin QPO frequencies in the range 113 − 441 Hz . The presence of the soliton halo introduces an additional extended mass component, which modifies orbital motion in the inner accretion region. We find that the radial epicyclic frequency typically decreases by about 10 − 18 % , while the vertical frequency increases by 12 − 25 % , depending on the soliton parameters. These shifts have a direct impact on the predicted QPO signals. To test the model, we compare three standard interpretations of twin QPOs: forced resonance (FR), relativistic precession (RP), and epicyclic resonance (ER), using a Bayesian MCMC analysis over the parameter set ( M , r , ρ c , r c ). The results show consistent constraints across all systems, with ρ c / M 2 ∼ 0.10 − 0.21 and r c / M ∼ 0.009 − 0.17 , and upper limits reaching ρ c / M 2 ≲ 0.55 and r c / M ≲ 0.48. Among the tested models, the FR scenario provides the best overall agreement, including an excellent fit for GRS 1915+105 with χ F R 2 = 0.057 , and good consistency for GRO J1655-40 and XTE J1550-564. Overall, the results suggest that ULBDM in its solitonic core form can leave measurable imprints on QPOs and may offer a realistic way to probe ULBDM near black holes.
Errehymy et al. (2026) studied this question.