Energy extraction from NED-deformed rotating black holes via the Comisso-Asenjo reconnection process

Abstract

We study rotating black holes in general relativity coupled to nonlinear electrodynamics (NED), focusing on an axisymmetric solution with deformation parameter g. On the spherical seed, weak-field lensing via the Gauss-Bonnet method and the shadow radius yield a spin-insensitive bound by enforcing a conservative ~10% tolerance on the Sgr A* ring size, namely g/M \lesssim 1.26. In the eikonal regime we derive analytic quasinormal-mode shifts, even in g, and obtain an independent ceiling consistent with the shadow constraint. For the rotating geometry, we provide closed-form ZAMO scalars, chart horizons and ergoregion, and analyze equatorial geodesics (photon orbits and ISCO). We then formulate in the ZAMO frame the Comisso-Asenjo reconnection channel, identify the negative-energy window, and integrate the extracted power over the allowed radii; from the tolerated fractional departure from the Kerr power we define a spin-dependent extraction bound g_δ(a|σ_0,ξ). Taken together, the QNM/shadow ceiling and the extraction bound appreciably narrow the admissible region for g/M in the (a/M, g/M) plane, so even within our deliberately simplified, single-layer equatorial setup, the two complementary probes already provide informative constraints on NED deformations, testable with present data and upcoming horizon-scale and ringdown campaigns.