2025/01/20 by Khadije Jafarzade, Jafarzade, khadije, M. Ghasemi-Nodehi +5 · 3 citations
Engineering · Physics and Astronomy · #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #Instrumentation and Methods for Astrophysics (astro-ph.IM) #Magnetic confinement fusion research #Superconducting Materials and Applications
paper · pdf · doi:10.48550/arxiv.2501.11692
openalex publication_date 2025/01/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The recent unveiling of the images of Sgr A* and M87* has significantly advanced our understanding of gravitational physics. In this study, we derive a class of Kerr-Taub-NUT metrics in the presence of a scalar field (KTNS). Treating these metrics as models for supermassive objects, we constrain the parameters using shadow size estimates done by observations of M87* and Sgr A* from the Event Horizon Telescope (EHT). Comparing the obtained results with M87* data, we show an upper limit on the NUT charge n such that the constraint on the shadow deviation from circularity ( ΔC ) will be fulfilled for n<0.5 , and this allowed range changes with a variation in other parameters. Additionally, our findings reveal that fast-rotating KTNS metrics are better candidates for supermassive M87* than slowly rotating ones. We continue our study by estimating parameters using Keck and VLTI observations of Sgr A* and find that the constraint on the fraction deviation δ is maintained within a certain range of the NUT charge such that the Keck bound is satisfied for n<0.41 . In contrast, the VLTI bound can be fulfilled for n>0.34 . Finally, we investigate weak gravitational lensing using the Gauss-Bonnet theorem and illustrate that all model parameters increase the deflection angle, causing light rays to deviate more significantly near fast-rotating KTNS objects.