Testing charged Simpson-Visser-AdS spacetimes with twin-peak QPOs
In this manuscript, we study circular geodesics and twin-peak high-frequency quasi-periodic oscillations (HF-QPOs) in the charged Simpson--Visser--anti-de Sitter (AdS) spacetime, which depends on a charge parameter $Q$, a regularization scale $b$ and an AdS radius $l$. Written in terms of the areal radius $R=\sqrt{r^{2}+b^{2}}$, 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, so $b$ enters the epicyclic spectrum only through a factor $1-b^{2}/R^{2}$ in the radial frequency. We give this frequency and the ISCO condition in closed form. We then fit the relativistic-precession model to the HF-QPO pairs of GRO~J1655$-$40 and XTE~J1550$-$564, with their dynamical masses included as Gaussian priors. The Schwarzschild limit gives $χ^{2}=32.9$ for two degrees of freedom. One additional deformation removes this tension: $Q/M=0.814^{+0.059}_{-0.074}$ at fixed $l=100M$, or $l=40.6^{+6.2}_{-4.8}\,M$ at $Q=0$, both with $χ^{2}\simeq0.13$. These two solutions lie on a single degeneracy valley in the $(Q,l)$ plane, and, at $l=100M$, $b$ is left unconstrained up to $b\simeq3.9M$ (68\%), a limit set by the charge prior rather than by the data. A Kerr black hole with spin $a\simeq0.3$--$0.4$ reproduces the same pairs, so the inferred deformation most likely absorbs the spin neglected by the static metric. Our results therefore describe degeneracies among orbital-frequency deformations; they are not a measurement of an electric charge or of a cosmological constant.