Sgr A* Shadow Study with KTN Space Time and Investigation of NUT Charge Existence

TL;DR

This study uses shadow observations of Sgr A* to constrain the NUT charge in KTN spacetime, finding limited ranges for its existence and suggesting that naked singularities are unlikely given current observational uncertainties.

Contribution

It provides the first constraints on the NUT charge of Sgr A* using shadow data and explores the implications for KTN black holes and naked singularities.

Findings

NUT charge constrained between -0.5 and 0.5 for certain black hole models.

Schwarzschild-like and slowly rotating KTN black holes are excluded at specific viewing angles.

Naked singularities in Sgr A* are unlikely considering shadow size uncertainties.

Abstract

In this paper, I investigate the existence of the NUT charge through the KTN spacetime using shadow observations of Sgr A*. I report that the range of my constraint for the NUT charge is between $-$0.5 and 0.5 for Schwarzschild-like and very slowly rotating KTN black holes. This range extends to 1.5 for spins up to $-$2 and $-$1.5 for spins up to 2 based on Keck observations for both 40$^\circ$ and 10$^\circ$ viewing angles. For VLTI observations, Schwarzschild-like and very slowly rotating KTN black holes are excluded for a 40$^\circ$ viewing angle, and the NUT charge is constrained to a very narrow range for a 10$^\circ$ viewing angle. I report that the possibility of having KTN naked singularities in Sgr A* is small, considering the uncertainties in the shadow size.