Superradiant evolution of the shadow and photon ring of Sgr A$^\star$

Abstract

Ultra-light bosons can affect the dynamics of spinning black holes (BHs) via superradiant instability, which can lead to a time evolution of the supermassive BH shadow. We study prospects for witnessing the superradiance-induced BH shadow evolution, considering ultra-light scalar, vector, and tensor fields. We introduce two observables sensitive to the shadow time-evolution: the shadow drift, and the variation in the azimuthal angle lapse associated to the photon ring autocorrelation. The two observables are shown to be highly complementary, depending on the observer's inclination angle. Focusing on the supermassive object Sgr A we show that both observables can vary appreciably over human timescales of a few years in the presence of superradiant instability, leading to signatures which are well within the reach of the Event Horizon Telescope for realistic observation times (but benefiting significantly from extended observation periods), and paving the way towards probing ultra-light bosons in the ∼ 10 −17 eV mass range.

Shape of higher-order images of equatorial emission rings around a Schwarzschild black hole: Analytical description with polar curves

“…In 2019, the Event Horizon Telescope has been presented the shadow of supermassive black hole in the M87 galaxy [59][60][61][62][63][64][65][66][67] (see also recent results about Sgr A* [68][69][70][71][72][73]). After that, attention has been attracted to the study of higher-order photon rings which can be expected in a more detailed image, being concentrated near the edge of the black hole shadow [74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92]. These rings are lensed images of the luminous matter surrounding the black hole.…”

Probing a non-linear electrodynamics black hole with thin accretion disk, shadow, and deflection angle with M87* and Sgr A* from EHT

“…the metric function given in equation ( 14) corresponds to a black hole with mass and charge-like terms. As per equation (14), the metric function remains finite at the origin r = 0, hence it is regular at m 0 = 0. Figure 1 shows the plot of the metric function (12) with G N = 1 for the different values of NLE parameter β in left and magnetic charge q in right with fixing other one to unity as given in [98].…”

Probing Our Universe’s Past Using Earth’s Geological and Climatological History and Shadows of Galactic Black Holes

“…Currently, the observation of the M87 shadow and of the SgrA* [75][76][77] is the best that we can get. There exists a large stream of promising works for the shadows of black holes even corresponding to these two galactic black holes, see for example [54][55][56][57][58][59][60][61] and references therein. The M87 black hole exists at z = 0.004283 thus due to the limitations on the resolution of VLBI techniques at high redshifts, our proposal cannot be observationally verified at present time, but rather it is a far future proposal.…”

“…As we show, the photon orbits around supermassive McVittie black holes are directly affected by a pressure singularity, thus this may have definable features on their shadow. The shadows of supermassive black holes are gradually developing to be quite fruitful for new physics discoveries, see for example [54][55][56][57][58][59][60][61] and references therein.…”