Finite-range hair from a nonlocal matter sector: charged Yukawa black holes

Abstract

{ We construct a new exact charged, static and spherically symmetric black-hole solution of the Einstein--Maxwell equations with an additional anisotropic matter sector, whose metric is the Reissner--Nordström geometry endowed with a Yukawa-type contribution. The Yukawa term is exponentially screened: it is visible in the strong-field region but carries no independent asymptotic charge. We obtain an analytic parametrization of the extremal curve, identify the condition for higher-order degenerate horizons, characterize the curvature singularity and establish the weak, null, dominant and strong energy conditions. We further study the horizon thermodynamics, including the conjugate variables associated with the amplitude and range of the Yukawa sector and the corresponding generalized Smarr relation. The photon sphere, shadow, ray-traced appearance and quasinormal ringdown are then analyzed, with quasinormal frequencies computed through the sixth-order WKB expansion and confirmed, overtones included, by an independent spectral method. {Confronting the model shadow with Event Horizon Telescope measurements of M87* and Sgr A* constrains the finite-range sector directly, favoring its strongly screened, near-Reissner--Nordström regime.} This provides a unified geometric and phenomenological characterization of finite-range charged black-hole hair in ordinary Einstein gravity. }