Black hole horizon around a relativistic star

TL;DR

This paper investigates the properties of a black hole horizon around a relativistic star, analyzing how the black hole's mass and entropy depend on the observer's position and the star's parameters.

Contribution

It provides a detailed analysis of the black hole horizon structure around a star, highlighting observer-dependent mass and entropy characteristics.

Findings

Black hole mass depends on observer position outside the star.

Entropy remains proportional to the area, consistent with the Bekenstein-Hawking formula.

Geometry remains Schwarzschild despite the black hole presence.

Abstract

A star surrounded by a black hole generated by it is analyzed. For an outer static observer the black hole mass (and radius) depends on his position in the gravitational field of the star. In spite of the black hole presence, the geometry remains that of Schwarzschild. For an inner observer the black hole mass is constant and depends on the star's mass $m$ and radius $R$. The entropy for $r > R$ is one quarter of the area and is constant for $r < R$.