Image of a regular phantom compact object and its luminosity under spherical accretions

Abstract

We have studied the black hole shadow and its luminosity for a static and regular phantom black hole under the static spherical accretion and the infalling spherical accretion, respectively.Comparing with the usual Schwarzschild black hole, the presence of phantom hair yields the larger black hole shadow and the darker image. In both spherical accretion models, with the increase of phantom parameter, the maximum luminosity occurred at photon ring and the brightness of the central region in the shadow decrease, but in the region far from the shadow, the luminosity of image slightly increases. This implies that the phantom hair is imprinted on both the shadow radius and the intensity of the electromagnetic flux radiation around black hole.

Photon Spheres and Spherical Accretion Image of a Hairy Black Hole

“…3 The dark region inside the bright ring refers to the black hole shadow, whose intensity does not vanish since part of the radiation of the accretion flow inside the photon sphere can escape to infinity. Note that this image is quite similar to those given in [12,[30][31][32][33].…”

“…To tentatively answer this question, we studied images of an accretion flow around the hairy black holes in the single-and double-peak potential cases. When the effective potential has a single peak, there is only one unstable photon sphere appearing as a bright ring at the edge of the black hole shadow, which is quite similar to various static black holes considered in [12,[30][31][32][33]. While for the double-peak potential, there exist two unstable photon spheres of different sizes.…”

Optical appearance of Einstein-Æther black hole surrounded by thin disk

“…Thus they will affect the optical appearance of the black hole. According to it, many accretion models have been proposed, such as the thin disk accretion [12,43,52,53], geometrically thick accretion [43], spherically symmetric accretion [54][55][56][57], heavy accretion [58], and so on. We should note that, with the accretion material extending to the event horizon, the dark region of the black hole image will be confined into a region, called the inner shadow, smaller than the black hole shadow.…”

Photon Ring and Observational Appearance of a Hairy Black Hole

“…Interestingly, it was argued in [43][44][45] that naked singularities can cast a shadow in the absence of the photon sphere. Furthermore, the EHT observation can also be applied to impose constraints on the cosmological parameters [46][47][48][49][50][51] and the size of extra dimensions [52][53][54], test the equivalence principle [55][56][57], and probe some fundamental physics issues including dark matter [21,[58][59][60][61][62][63] and dark energy [64][65][66][67].…”

“…In fact, the realistic image is a result of the complex interactions between the strong gravitational lensing of the black hole and the electromagnetic plasma in the accretion flow, which requires intensive numerical general relativistic magnetohydrodynamic (GRMHD) simulations [68]. Nevertheless, simplified accretion models usually suffice to capture major features of black hole images, and hence have been widely investigated in the literature, e.g., spherical accretion flows [26,43,63,65,66,69], thin or thick accretion disks [70][71][72][73][74][75][76][77]. In particular, the authors in [72] considered the emission from an optically and geometrically thin disk around a Schwarzschild black hole, which is divided into three classes by the number m of half-orbits that an emitted photon completes around the black hole before reaching the observer: the direct emission (m ≤ 1), the lensing ring (m = 2) and the photon ring (m ≥ 3).…”