Dynamics of null particles and shadow for general rotating black hole

Meng, Kun; Fan, Xi-Long; Li, Song; Han, Wen-Biao; Zhang, Hongsheng

doi:10.1007/jhep11(2023)141

Cited by 4 publications

(2 citation statements)

References 100 publications

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“…The most relevant comparisons are those of Kocherlakota et al (2021), the Event Horizon Telescope Collaboration et al (2022b), andVagnozzi et al (2023), which directly infer limits on a number of the alternative spacetimes we consider here. In addition, limits that incorporate potential shape characterizations have appeared in the literature (see, e.g., Meng et al 2022Meng et al , 2023Sui et al 2023), though currently, EHT-derived limits on the departure from circularity remain dominated by systematic uncertainties (Tiede et al 2022a(Tiede et al , 2022b.…”

Section: Observational Implicationsmentioning

confidence: 99%

Photon Rings and Shadow Size for General Axisymmetric and Stationary Integrable Spacetimes

Salehi,

Broderick,

Georgiev

2024

ApJ

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There are now multiple direct probes of the region near black hole horizons, including direct imaging with the Event Horizon Telescope (EHT). As a result, it is now of considerable interest to identify what aspects of the underlying spacetime are constrained by these observations. For this purpose, we present a new formulation of an existing broad class of integrable, axisymmetric, stationary spinning black hole spacetimes, specified by four free radial functions, that makes manifest which functions are responsible for setting the location and morphology of the event horizon and ergosphere. We explore the size of the black hole shadow and higher-order photon rings for polar observers, approximately appropriate for the EHT observations of M87*, finding analogous expressions to those for general spherical spacetimes. Of particular interest, we find that these are independent of the properties of the ergosphere, but do directly probe the free function that defines the event horizon. Based on those expressions, we extend the nonperturbative, nonparametric characterization of the gravitational implications of various near-horizon measurements to spinning spacetimes. Finally, we demonstrate this characterization for a handful of explicit alternative spacetimes.

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Section: Observational Implicationsmentioning

confidence: 99%

Photon Rings and Shadow Size for General Axisymmetric and Stationary Integrable Spacetimes

Salehi,

Broderick,

Georgiev

2024

ApJ

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“…Laor proposed a formulation for calculating line profiles emitted from accretion disks around rotating black holes, highlighting the preponderance of a flux emanating from the disk's inner realm and manifesting as a blue shift in the line peak [17]. The depiction of accretion disks in various modified gravity contexts of black holes has prompted extensive scholarly inquiries [18][19][20][21][22]. Delving into Rastall's theoretical framework to understand black holes enriches the comprehension of this alternative gravitational paradigm.…”

Section: Introductionmentioning

confidence: 99%

Rastall gravity: accretion disk image in the context of radiation fields and visual transformations compared to Reissner-Nordström black hole*

Huang 黄,

Guo 郭,

Liang 梁

et al. 2024

Chinese Phys. C

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Our study investigates the astronomical implications of Rastall gravity, particularly its behavior amidst a radiation field compared to Reissner-Nordstr"{o}m (RN) black holes. Our research delineates a crucial correlation between the dynamics of the accretion disk and the parameters Q and N_{\rm r}, which aptly reflect the influence of spacetime metrics on the disk's appearance. Elevated electric charge Q prompts contraction in the disk’s orbit due to enhanced gravitational effects, while higher N_{\rm r} values lead to outward expansion, influenced by the radiation field's attributes. Interestingly, the charged black holes surrounded by radiation fields display distinct visual disparities from RN black holes. Brightness decreases and expansion occurs within the accretion disk's innermost stable circular orbit with rising N_{\rm r} values. Our study also reveals the process by which the accretion disk transitions from a conventional disk-like structure to a hat-like form at different observation angles, with the redshift effect gradually intensifying. Moreover, the results of the Rastall gravity radiation field we consider are consistent with the constraints of the host galaxy's gravitational lensing on the Rastall gravity parameters, enhancing the consistency between theoretical predictions and actual observations.

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Images of hairy Reissner–Nordström black hole illuminated by static accretions

Meng,

Kuang,

Wang

et al. 2024

Eur. Phys. J. C

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In this paper, we investigate the shadow and optical appearance of the hairy Reissner–Nordström (RN) black hole illuminated by two toy models of static accretion. The hairy RN black hole was constructed in the gravitation decoupling approach to describe the deformation of a Schwarzschild black hole due to the inclusion of additional arbitrary source (scalar field, tensor field, fluidlike dark matter, etc.). So it is characterized by the parameters: mass (M), deformation factor ($$\alpha $$ α ), electric charge (Q) and the additional hairy charge ($$l_o$$ l o )., differentiating from the case in RN black hole. Though the specific background theory that results in this hairy RN black hole is still tricky, here we shall focus on the novel observable features introduced by the hair of this black hole. First, we find that for the hairy RN black hole, the event horizon, radius of photon sphere and critical impact parameter all increase as the increasings of Q and $$l_o$$ l o , but decrease as $$\alpha $$ α grows. Furthermore, the three characterized parameters are found to have significant effects on the photon trajectories, and shadows as well as images of the hairy RN black hole surrounded by the static accretion disk and spherical accretion, respectively. In particular, both Q and $$l_o$$ l o have mutually reinforcing effects on the optical appearance and shadows of the hairy RN black hole, which implies that we may not distinguish the electric charge and hairy charge from the shadow and image of black hole in this scenario. Additionally, because of the competing effects of the charge parameters ($$Q, l_o$$ Q , l o ) and the deviation parameter $$\alpha $$ α on the observed intensities of brightness, the optical appearance between the hairy RN black hole and RN black hole could have degeneracies, indicating the indistinguishability. Our current results contribute more to the phenomenal aspects which could be helpful to build the background theory of this hairy RN black hole.

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Dynamics of null particles and shadow for general rotating black hole

Cited by 4 publications

References 100 publications

Photon Rings and Shadow Size for General Axisymmetric and Stationary Integrable Spacetimes

Photon Rings and Shadow Size for General Axisymmetric and Stationary Integrable Spacetimes

Rastall gravity: accretion disk image in the context of radiation fields and visual transformations compared to Reissner-Nordström black hole*

Images of hairy Reissner–Nordström black hole illuminated by static accretions

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