Testing Rotating Regular Metrics with EHT Results of Sgr A*

Kumar, Rahul; Ghosh, Sushant G.; Maharaj, S. D.

doi:10.3847/1538-4357/ac9623

Cited by 54 publications

(9 citation statements)

References 115 publications

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“…The most direct observable manifestation of the null spherical orbital motion, in the vicinity of a BH, is the formation of shadow [1,62,63] -a two dimensional dark region in the observer's sky on a bright background, outlined by a series of asymptotically spaced ring like structures that mark the shadow boundary [64,65]. BH shadows in both GR [49,52,[66][67][68][69][70] and MoGs [28,32,45,46,48,[71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88][89], have served as a widely used tool to estimate the parameters associated with the BHs [46,48,49,90], besides, the shadow shape and size can probe the various MoGs and constrain them [32,44,46,48,53,80,[91]…”

Section: Constraining Dark Matter With Eht Resultsmentioning

confidence: 99%

“…where Σ = r 2 +a 2 cos 2 θ and ∆ = r 2 +a 2 −2m(r)r. Here is a the spin parameter and the metric (7) go over to Kerr spacetime in absence of the surrounding PFDM (k = 0). In general, the metric ( 7) is a prototype non-Kerr spacetime that represents Kerr-Newman [43] and Kerr [2] spacetimes, respectively, when m(r) = M − Q 2 /2r and m(r) = M ; further, depending on m(r), the metric (7) can also represent a variety of BHs viz., Hayward [44,45], Bardeen [44,45], Ghosh-Culetu [44,45], Ghosh-Kumar [45], rotating Quintessence [20], hairy Kerr [46,47], rotating Horndeski [48]. Indeed, dark matter makes up a major portion of the Universe's energy density [33] and any observational constraints placed on k would be an essential step in fundamental physics.…”

Section: Equations Of Motion In Rotating Pfdm Spacetimementioning

confidence: 99%

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Astrophysical consequences of dark matter for photon orbits and shadows of supermassive black holes

Anjum¹,

Afrin²,

Ghosh³

2023

Preprint

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We consider Kerr black holes (BHs) surrounded by perfect dark fluid matter (PFDM), with an additional parameter (k) because of PFDM, apart from mass (M ) and rotation parameter (a) -the rotating PFDM BHs. We analyze the photon orbits around PFDM BHs and naked singularities (NSs) and emphasise the effect of PFDM on photon boomerangs. Interestingly, the azimuthal oscillations first increase and then decrease for retrograde orbits, whereas they first decrease and then increase for prograde orbits, with increasing k. Unlike in the Kerr NSs, photon boomerangs can form around rotating PFDM NSs. We use the Event Horizon Telescope (EHT) observational results for Schwarzschild shadow deviations of M87* and Sgr A*, δM87 * = −0.01 ± 0.17 and δSgrA * = −0.08 +0.09 −0.09 (VLTI), −0.04 +0.09 −0.10 (Keck), to report the upper bounds on the PFDM parameter: 0 ≤ k ≤ 0.0792M and k max ∈ [0.0507M, 0.0611M ] respectively. Together with the EHT bounds on the shadows of Sgr A * and M87 * , our analysis concludes that a substantial part of the rotating PFDM BH parameter space agrees with the EHT observations. Thus, one must consider the possibility of the rotating PFDM BHs being strong candidates for the astrophysical BHs.

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Section: Constraining Dark Matter With Eht Resultsmentioning

confidence: 99%

Section: Equations Of Motion In Rotating Pfdm Spacetimementioning

confidence: 99%

Astrophysical consequences of dark matter for photon orbits and shadows of supermassive black holes

Anjum¹,

Afrin²,

Ghosh³

2023

Preprint

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“…Theoretical studies of BH shadows for different gravity models and BH solutions can be found in . After the first ever observation of the BH shadows of M87 and Sgr A * in 2019 [19] and in 2022 [21], the observations have been developed by various authors [91][92][93][94][95][96][97][98].…”

Section: Introductionmentioning

confidence: 99%

Exploring the shadow of a rotating charged ModMax black hole

Karshiboev,

Atamurotov,

Abdujabbarov

et al. 2024

Commun. Theor. Phys.

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The research presented in this paper discusses the impact that the parameters of charge ($Q$) and screening factor ($\gamma$) have on properties of the horizon and silhouette of rotating charged ModMax black holes which were reviewed in [Eur.~Phys.~J.~C (2022)~82:1155]recently, building upon previous findings in the field. Furthermore, the study explores the behavior of null geodesics, which can help us better understand the apparent shape of the black hole's silhouette, as well as the distortion parameter and approximate radii of the silhouette that are influenced by the aforementioned parameters and there are some values of parameter $Q$ which corresponds to data from EHT. Notably, we explore the distortion parameter and approximate radii of the silhouette, revealing that while an increase in $\gamma$ leads to a growth in silhouette radius ($R_s$), it simultaneously reduces the distortion rate ($\delta_s$). Conversely, heightened $Q$ charge results in a reduction of $R_s$ accompanied by an increase in $\delta_s$. Lastly, the paper analyzes the effects of black hole's parameters on the effective potential and energy emission that the peak of the energy emission rate experiences a decline as the screening factor ($\gamma$) increases, while it ascends with higher values of the charge parameter ($Q$).

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“…The EHT observation of M87 * and Sgr A * presents a new powerful technique to test the BH metric gravitationally in the strong-field regime and also provides an exceptional way to constrain the various BH parameters and to test the underlying associated theories of gravity (Afrin et al 2021;Kocherlakota et al 2021;Ghosh et al 2021;Akiyama 2022f;Islam et al 2022;Kumar et al 2022;Walia et al 2022;Sengo et al 2022). Therefore, the EHT results offer a considerable recent complement to the set of observations that probe the strong-field regime of gravity, namely the LIGO/Virgo detection of gravitational waves from stellar-mass BH mergers (Abbott et al 2016).…”

Section: Introductionmentioning

confidence: 99%

“…(de Vries 2000;Falcke et al 2000;Shen et al 2005;Yumoto et al 2012;Atamurotov et al 2013;Abdujabbarov et al 2015;Johannsen et al 2016;Cunha & Herdeiro 2018;Chael et al 2021;Afrin & Ghosh 2022b) and modified theories of gravity(Amarilla et al 2010;Johannsen & Psaltis 2011;Papnoi et al 2014;Amir et al 2018;Mizuno et al 2018;Kumar et al 2020d;Allahyari et al 2020;Afrin et al 2021;Brahma & Chen 2021;Ghosh et al 2021;Afrin & Ghosh 2022a;Islam et al 2022;Junior et al 2022;Kuang et al 2022;Kumar et al 2022;Walia et al 2022; Sengo et al 2022;Vagnozzi et al 2022). The fact that the BH shadows carry information about the strong-field properties of the spacetime suggests that we can use them for performing strong-field gravitational tests(Johannsen & Psaltis 2010;Baker et al 2015;Cunha & Herdeiro 2018).…”

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confidence: 99%

Tests of Loop Quantum Gravity from the Event Horizon Telescope Results of Sgr A*

Afrin

Vagnozzi

Ghosh

2023

ApJ

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The Event Horizon Telescope (EHT) collaboration’s image of the compact object at the Galactic center is the first direct evidence of the supermassive black hole (BH) Sgr A*. The shadow of Sgr A* has an angular diameter d sh = 48.7 ± 7 μas with fractional deviation from the Schwarzschild BH shadow diameter δ = − 0.08 − 0.09 + 0.09 , − 0.04 − 0.10 + 0.09 (for the VLTI and Keck mass-to-distance ratios). Sgr A*'s shadow size is within 10% of Kerr predictions, equipping us with yet another tool to analyze gravity in the strong-field regime, including testing loop quantum gravity (LQG). We use Sgr A*'s shadow to constrain the metrics of two well-motivated LQG-inspired rotating BH (LIRBH) models characterized by an additional deviation parameter L q , which recover the Kerr spacetime in the absence of quantum effects (L q → 0). When increasing the quantum effects through L q , the shadow size increases monotonically, while the shape gets more distorted, allowing us to constrain the fundamental parameter L q . We use the astrophysical observables shadow area A and oblateness D to estimate the BH parameters. It may be useful in extracting additional information about LIRBHs. While the EHT observational results completely rule out the wormhole region in LIRBH-2, a substantial parameter region of the generic BHs in both models agrees with the EHT results. We find that the upper bounds on L q obtained from the shadow of Sgr A*—L q ≲ 0.0423 and L q ≲ 0.0821 for the two LIRBHs, respectively—are more stringent than those obtained from the EHT image of M87*.

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Testing Rotating Regular Metrics with EHT Results of Sgr A*

Abstract: The Event Horizon Telescope (EHT) observation unveiled the first image of supermassive black hole Sgr A* showing a shadow of diameter θ sh = 48.7 ± 7 μas with fractional deviation from the Schwarzschild black hole shadow diameter δ = − 0.08 … Show more

Cited by 54 publications

References 115 publications

Astrophysical consequences of dark matter for photon orbits and shadows of supermassive black holes

Astrophysical consequences of dark matter for photon orbits and shadows of supermassive black holes

Exploring the shadow of a rotating charged ModMax black hole

Tests of Loop Quantum Gravity from the Event Horizon Telescope Results of Sgr A*

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