Timing of echoes in electromagnetic radiation from hot spots orbiting a Kerr black hole impostor

Abstract

We investigate the light curve of an isolated bright spot in a Keplerian orbit around a Kerr black hole candidate to probe possible deviations from the standard event-horizon picture. In particular, we explore the presence of a reflective surface, namely a "mirror" near the horizon, and its observable consequences. We present estimates on the time delays of the echoes of electromagnetic radiation from the mirror or some other reflecting area related to black hole mimickers. Our results show that photon reflections from such a surface imprint distinct late-time features in the light curve, producing an electromagnetic analogue of gravitational wave echoes. For lower values of the spin, the reflected signal appears within the same orbital period and leads to a noticeable enhancement of the flux. In contrast, for higher spins, the effect emerges only after several orbits, giving rise to a characteristic echo-wave train. These features provide a potential observational signature of horizon-scale modifications in compact objects.

References in corpus (21)

• First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole
• The Nuclear Spectroscopic Telescope Array (NuSTAR) Mission
• First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
• Black Holes: Complementarity or Firewalls?
• Testing the nature of dark compact objects: a status report
• First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon
• Dynamical Boson Stars
• Stable gravastars - an alternative to black holes?
• First M87 Event Horizon Telescope Results. VII. Polarization of the Ring
• Detection of orbital motions near the last stable circular orbit of the massive black hole SgrA*
• Echoes from the Abyss: Tentative evidence for Planck-scale structure at black hole horizons
• The observational evidence for horizons: from echoes to precision gravitational-wave physics
• Tests for the existence of horizons through gravitational wave echoes
• Gravitational Condensate Stars: An Alternative to Black Holes
• Profiles of emission lines generated by rings orbiting braneworld Kerr black holes
• Scattering of particles by neutron stars: Time-evolutions for axial perturbations
• Distinguishing black holes and wormholes with orbiting hot spots
• X-ray iron line variability for the model of an orbiting flare above a black hole accretion disc
• Radiative properties of magnetic neutron stars with metallic surfaces and thin atmospheres
• Light curve of a source orbiting around a black hole: A fitting-formula
• A Hot Spot Model for Black Hole QPOs