Profiled spectral lines generated by Keplerian discs orbiting in the Bardeen and Ayon-Beato-Garcia spacetimes

TL;DR

This paper analyzes spectral line profiles and frequency-shift maps of Keplerian discs around Bardeen and ABG spacetimes, revealing distinctive observational signatures that differentiate these regular black hole and no-horizon models from Schwarzschild black holes.

Contribution

It provides the first detailed comparison of spectral line profiles and frequency-shift maps in Bardeen and ABG spacetimes, highlighting observable differences from Schwarzschild black holes.

Findings

Differences in spectral profiles are more pronounced in no-horizon spacetimes.

Distinct signatures allow differentiation of Bardeen and ABG spacetimes at known inclination angles.

Ghost image contributions increase with spacetime charge parameter.

Abstract

Shape and frequency-shift map of direct and indirect images of Keplerian discs orbiting in Bardeen and Ayon-Beato-Garcia (ABG) black hole and no-horizon spacetimes are determined. Then profiles of spectral lines generated in the innermost parts of the Keplerian discs in the Bardeen and ABG spacetimes are constructed. The frequency-shift maps and profiled spectral lines are compared to those generated in the field of Schwarzschild black holes and possible observationally relevant signatures of the regular black hole and no-horizon spacetimes are discussed. We demonstrate that differences relative to the Schwarzschild spacetimes are for the no-horizon spacetimes much more profound in comparison to the regular black hole spacetimes and increase with increasing charge parameter of the spacetime. The differences are stronger for small and large inclination angles than for mediate ones. For the no-horizon spacetimes, the differences enable to distinguish the Bardeen and ABG spacetime, if inclination angle to the distant observer is known. We also show that contribution of the so called ghost images to the profiled lines increases with increasing charge parameter of the spacetimes.