An analysis of the high-frequency quasi-periodic oscillations (HF-QPOs) observed in two X-ray binaries, GRO J1655−40 and XTE J1550−564, shows that the deformations of the charged Simpson-Visser spacetime with an AdS term that best fit the data cannot be interpreted as a measurement of electric charge or of the cosmological constant. The work, available on arXiv, concludes that what the fit absorbs is in fact the black hole spin, which the static metric used does not account for.

In the charged Simpson-Visser–AdS spacetime, which depends on a charge parameter Q, a regularization scale b and an AdS radius l, the specific energy, angular momentum, Keplerian frequency and innermost stable circular orbit (ISCO) of test particles coincide with those of the Reissner-Nordström–AdS black hole when written in terms of the areal radius R = √(r² + b²). The scale b enters the epicyclic spectrum only through a factor 1 − b²/R² in the radial frequency, which the authors give in closed form together with the ISCO condition.

Applying the relativistic-precession model to the HF-QPO pairs of both binaries, with dynamical masses as Gaussian priors, the Schwarzschild limit leaves χ² = 32.9 for two degrees of freedom, a clear sign of tension. One additional deformation removes it: Q/M = 0.814 (+0.059 −0.074) at fixed l = 100 M, or l = 40.6 (+6.2 −4.8) M at Q = 0, both with χ² ≈ 0.13. The two solutions lie on a single degeneracy valley in the (Q, l) plane, and at l = 100 M the scale b is left unconstrained up to b ≈ 3.9 M (68 %), a limit set by the charge prior rather than by the data.

A Kerr black hole with spin a ≈ 0.3–0.4 reproduces the same frequency pairs, leading the authors to conclude that the inferred deformation most likely absorbs the spin neglected by the static metric. The results therefore describe degeneracies among orbital-frequency deformations, not a measurement of electric charge or of a cosmological constant, and highlight the difficulty of discriminating alternative metrics with only two QPO peaks.