Black hole shadow: Experimental test of different models and shadow of dynamical Hayward black hole

Abstract

Recent observations of black hole shadows have revolutionized our ability to probe gravity in extreme environments. This manuscript presents a novel analytic model of the shadow of a dynamical Hayward black hole. We show that under some choice of mass and regularization functions, this spacetime admits a homothetic Killing vector, which allows the reduction of the second-order differential equations of motion to the firstorder ones. After that, we introduce the coordinate transformation to conformally-static coordinates and introduce a new conserved quantity along null geodesics. We prove that in the dynamical case the regularization parameter always decreases the radius of a photon sphere. Inspired by the experimental data obtained by the Event Horizon Telescope Collaboration, we compare the obtained images of Sagittarius A* with a black hole shadow in Reissner–Nordstrom, Bardeen and Hayward black holes, respectively.

Keywords

• black hole
• photon sphere
• mass-dependent
• shadow
• dynamical Hayward black hole