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Probing the Shadow Image of the Sagittarius A* with Event Horizon Telescope

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arxiv 2202.00588 v1 pith:PNMPYJUE submitted 2022-01-29 gr-qc astro-ph.GA

classification gr-qcastro-ph.GA
keywords nakedblackholeimagesingularitysupermassivebaselinecompact
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abstract

Recent observations of the Milky-way galactic center at various frequencies suggest a supermassive compact object. Generally, that supermassive compact object is assumed to be a `Black Hole', having more than four million solar masses. In this work, we study the observational appearance at $230$ GHz and probe the nature of Sagittarius-A* (Sgr A*) as the naked singularity. Here, we consider the first type of Joshi-Malafarina-Narayan (JMN-1) and Janis-Newman-Winicour (JNW) naked singularity spacetimes which are anisotropic fluid solutions of the Einstein field equations. Motivated by radiatively inefficient accretion flows (RIAF), we use an analytical model for emission and absorption coefficients to solve the general relativistic radiative transfer equation. The resulting emission is then utilized to generate images to predict the nature of the Sgr A* with synthetic Very Long Baseline Interferometry (VLBI) images from current and future Event Horizon Telescope (EHT) arrays. Three different EHT array configurations are being used to simulate the models of naked singularities and a black hole. This may have little effect on the baseline, but it would increase the u-v plane gridding, making it feasible to capture a better-resolved image. Therefore, it is quite interesting and useful for the upcoming shadow image of the Sgr A* to predict whether it is a supermassive black hole or a naked singularity.

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Cited by 3 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Optical appearance of regularized compact objects without an exterior photon sphere

    gr-qc 2025-12 conditional novelty 5.0 of 10

    Simpson–Visser regularization of null-singularity metrics yields core-controlled shadows without a photon sphere that can mimic Schwarzschild when the regularization length L≈4M.

  2. Time Delay of Pulsar Signals in Astrophysical Black Hole Spacetimes

    gr-qc 2025-06 conditional novelty 5.0 of 10

    Pulsar time delays are computed for Kerr, deformed Kerr (Johannsen-Psaltis), and rotating Janis-Newman-Winicour spacetimes, producing model-dependent signatures of up to about 15 seconds.

  3. Shadow Formation Conditions Beyond the Kerr Black Hole Paradigm

    gr-qc 2025-09 reject novelty 3.0 of 10

    A shadow can form without a photon sphere if the effective potential for null geodesics is finite and contains a region that traps or scatters light.

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