Broad and skewed iron Kα emission lines in the X‑ray spectra of accreting black holes encode key information about space-time geometry in the innermost disk regions. While relativistic reflection models that assume the Kerr metric have yielded spin measurements for dozens of black hole candidates, horizonless alternatives, particularly traversable “Kerr‑like” wormholes, can reproduce many observational signatures of black holes and thus challenge the interpretation of these data. We aim to develop and apply a new relativistic reflection framework that explicitly incorporates Kerr‑like wormhole geometries to predict the iron line distortions introduced by wormhole throat effects and assess the feasibility of distinguishing event horizons from horizonless throats using current and future X‑ray observations. Building on a custom ray‑tracing subroutine for Kerr-like wormhole space-times, we implemented two custom modules, for isolated δ‑function line profiles and for full rest‑frame reflection spectra, parameterized by spin, throat radius, and shape‐function coefficients. We computed a dense grid of line profiles over the wormhole parameter space, embedded them within multicomponent reflection models, and generated synthetic Nuclear Spectroscopic Telescope Array () spectra that incorporate realistic response matrices and backgrounds. By fitting these simulated data with canonical Kerr black hole based models and examining fit quality and residual structure, we quantified the deviations attributable to wormhole geometries. XSPEC kwline kwconv NuSTAR We find that Kerr-like wormholes systematically produce narrower Fe Kα lines with suppressed red wings and angle-dependent morphological shifts as the throat parameter, łambda, increases. In spectral fitting simulations of a high-flux 50 ks exposure (mocked with łambda=0. 9, a_*=0. 998), standard Kerr black hole convolution models () can effectively mimic the wormhole spectrum with high statistical precision. Conversely, fitting with the self-consistent, angle-dependent reflection model results in a formal statistical failure with pronounced structured residuals and unphysical parameter pegging, such as the emissivity index q_̊m in reaching its limit of 10. These results indicate that while Kerr-like wormholes and black holes exhibit significant observational degeneracy under simple convolutional modeling, they can be distinguished through more rigid, self-consistent reflection frameworks. NuSTAR kerrconv relxillCp We conclude that large-throat wormholes are potentially detectable in high-quality X-ray spectra, provided the analysis moves beyond post-processing approximations toward fully consistent relativistic reflection models.
Liu et al. (Tue,) studied this question.