General Approach on Shadow Radius and Photon Spheres in Asymptotically Flat Spacetimes and the Impact of Mass-Dependent Variations

TL;DR

This paper introduces a new analytic method for calculating photon sphere and shadow radius in asymptotically flat spacetimes, emphasizing mass-dependent effects and aiding future black hole observations.

Contribution

The paper presents a novel analytic approach for photon sphere and shadow radius calculations that simplifies analysis for complex metrics and incorporates mass-dependent variations.

Findings

New analytic method for photon sphere and shadow radius calculation

Insights into mass-dependent effects on black hole shadows

Potential for improved gravity tests with future observations

Abstract

Recent observations of black hole shadows have revolutionized our ability to probe gravity in extreme environments. This manuscript presents a novel analytic method to calculate, in leading-order terms, the key parameters of photon sphere and shadow radius. This method offers advantages for complex metrics where traditional approaches are cumbersome. We further explore the impact of black hole mass on the photon sphere radius, providing insights into black hole interactions with their surroundings. Our findings contribute significantly to black hole physics and gravity under extreme conditions. By leveraging future advancements in observations, such as the next-generation Event Horizon Telescope (ngEHT), this work paves the way for even more precise tests of gravity near black holes.