http://arxiv.org/abs/2206.02488
The Event Horizon Telescope (EHT), recently released the image of supermassive black hole Sgr A* showing an angular shadow diameter $d_{sh}= 48.7 \pm 7\,\mu$as, with an inferred black hole mass $M = 4.0^{+1.1}{-0.6} \times 10^6 M\odot $ and Schwarzschild shadow deviation $\delta = -0.08^{+0.09}{-0.09}~\text{(VLTI)},-0.04^{+0.09}{-0.10}~\text{(Keck)}$. The EHT image of Sgr A* is consistent with a Kerr black hole’s expected appearance and the results directly prove a supermassive black hole in the center of the Milky Way. The Kerr hypothesis, a strong-field prediction of general relativity (GR), may not hold in the theories of gravity that admit Kerr-like black holes having an additional deviation parameter arising from the underlying theory. Here, we use the EHT observational results of Sgr A* to investigate the constraints on the deviation parameter whereby, such a rotating Kerr-like black hole can be an astrophysical black hole candidate, paying attention to three leading models. Modelling Kerr-like black holes as supermassive black hole Sgr A*, we observe that for it to be a viable astrophysical black hole candidate, the EHT results of Sgr A* put more stringent constraints on the parameter space than those put by the EHT results of M87*. However, a systematic bias analysis shows Kerr-like black hole shadows may capture Kerr black hole shadows over a good part of the constrained parameter space, making Kerr-like and Kerr black holes indistinguishable and one can’t rule out a possibility of potential modifications of the Kerr metric or GR.
S. Ghosh and M. Afrin
Tue, 7 Jun 22
69/70
Comments: 13 pages, 4 figures, 1 table
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