Signatures of the accelerating black holes with a cosmological constant from the $\textrm{Sgr~A}^\star$ and $\textrm{M87}^\star$ shadow prospects

Understand

Recently, the Event Horizon Telescope (EHT) achieved the realization of an image of the supermassive black hole $\textrm{Sgr~A}^\star$ showing an angular shadow diameter $\mathcal{D}= 48.7 \pm 7\mu as$ and the fractional deviation $\mathbf{\delta} = -0.08^{+0.09}_{-0.09}~\text{(VLTI)},-0.04^{+0.09}_{-0.10}~\text{(Keck)}$, alongside the earlier image of $\textrm{M87}^\star$ with angular diameter $ \mathcal{D}=42 \pm 3 \mu as$, deviation $\mathbf{\delta}=-0.01^{+0.17}_{-0.17}$ and deviations from circularity estimated to be $\Delta \mathcal{C}\lesssim 10\%$.

• In addition, the shadow radii are assessed within the ranges $3.38 \le \frac{r_{\text{s}}}{M} \le 6.91$ for $\textrm{M87}^\star$ and $3.85 \le \frac{r_{\text{s}}}{M} \le 5.72$ as well as $3.95 \le \frac{r_{\text{s}}}{M} \le 5.92$ for $\textrm{Sgr~A}^\star$ using the Very Large Telescope Interferometer (VLTI) and Keck observatories, respectively.
• These values are provided with $1$-$\sigma$ and $2$-$\sigma$ measurements.
• Such realizations can unveil a better comprehension of gravitational physics at the horizon scale.