Measuring the shape of a black hole photon ring

Abstract

General relativity predicts that gravitational lensing near black holes will produce narrow "photon rings" on images. Building on recent work of Johnson, Lupsasca et al. focusing on circular rings, I calculate the long-baseline interferometric signature of a narrow feature of arbitrary shape and intensity. The shape information is contained in the oscillation frequencies of the complex visibility as a function of baseline length, for each baseline angle. These results raise the possibility of measuring the detailed shape of a photon ring and comparing to the precise predictions of general relativity.

v2 corrected some statements

References in corpus (2)

• Black Hole Shadows, Photon Rings, and Lensing Rings
• Lensing by Kerr Black Holes

Cited by in corpus (5)

• Images and photon ring signatures of thick disks around black holes
• Relating Black Hole Shadow to Quasinormal Modes for Rotating Black Holes
• The Black Hole Explorer: Photon Ring Science, Detection and Shape Measurement
• Is a black hole shadow a reliable test of the no-hair theorem?
• Fractal signatures of non-Kerr spacetimes in the shadow of light-ring bifurcations