Extended-Path Intensity Correlation: Microarcsecond Astrometry with an Arcsecond Field of View

TL;DR

This paper introduces Extended-Path Intensity Correlation (EPIC), a novel optical technique that enhances intensity interferometry for microarcsecond astrometry of bright celestial sources over arcsecond fields.

Contribution

The paper details the development and potential of EPIC, a new method that extends optical path length in intensity interferometry for high-precision differential astrometry.

Findings

EPIC can achieve microarcsecond resolution on bright sources.

The method enables differential astrometry of sources separated by up to a few arcseconds.

EPIC broadens the scope of intensity interferometry for various astrophysical applications.

Abstract

We develop in detail a recently proposed optical-path modification of astronomical intensity interferometers. Extended-Path Intensity Correlation (EPIC) introduces a tunable path extension, enabling differential astrometry of multiple compact sources such as stars and quasars at separations of up to a few arcseconds. Combined with other recent technological advances in spectroscopy and fast single-photon detection, a ground-based intensity interferometer array can achieve microarcsecond resolution and even better light-centroiding accuracy on bright sources of magnitude $m \lesssim 15$. We lay out the theory and technical requirements of EPIC, and discuss the scientific potential. Promising applications include astrometric lensing of stars and quasar images, binary-orbit characterization, exoplanet detection, Galactic acceleration measurements and calibration of the cosmic distance ladder. The introduction of the path extension thus significantly increases the scope of intensity interferometry while reaching unprecedented levels of relative astrometric precision.